Toward a Thaw in the Cambodia-Thailand Border Conflict

What’s new? Fighting between Cambodia and Thailand over a border dispute killed at least 150 people and displaced almost a million more in 2025. Now, the ceasefire between the two countries is fraying, while diplomacy has stalled.

Why does it matter? The 2025 combat was the costliest yet between the two countries and the worst confrontation ever between two members of the Association of South East Asian Nations. War could break out again if Bangkok and Phnom Penh do not improve relations.

What should be done? Leaders in Bangkok and Phnom Penh should work to normalise diplomatic ties, reconvene the Joint Boundary Commission in order to resume the surveys that will let the sides demarcate the land border, when circumstances allow, and cooperate on a program of demining affected areas.

Executive Summary

After two rounds of fighting in 2025 over a longstanding territorial dispute along their 800km land border, a ceasefire between Cambodia and Thailand is under strain, threatened by heightened nationalism on both sides and mutual allegations of violations. Tensions between the two countries resurfaced early in 2025, erupting into combat that dwarfed earlier clashes in scale. When the shooting stopped on 27 December, Thailand had the upper hand, holding most of the contested areas as well as slivers of Cambodian territory. In May, Bangkok withdrew from a 2001 bilateral agreement on how to resolve overlapping maritime claims, leading Phnom Penh to initiate compulsory conciliation – a non-binding international legal proceeding – under the UN Convention on the Law of the Sea. In turn, Thailand suspended participation in bilateral mechanisms on land border demarcation, leaving negotiations in limbo. To avoid more war, the two countries should put nationalist fervour to the side and overcome their mistrust, starting with restoring normal diplomatic ties and resuming efforts to jointly demarcate the land border.

Following an exchange of fire in May 2025 that killed a Cambodian soldier, fighting broke out along the border in late July. With Malaysian mediation, backed up by U.S. President Donald Trump’s vow to suspend trade talks with both countries so long as hostilities continued, the two sides agreed to a ceasefire after five days of combat. Tensions simmered over the following months, however, with regular confrontations between troops and a series of landmine explosions that wounded sixteen Thai soldiers. The ceasefire collapsed in November, and a second round of hostilities ensued, displacing almost a million people on both sides before halting with another truce, brokered this time with China’s help near year’s end.

The conflict is linked to domestic politics in both countries. Border tensions were pivotal in the disqualification from office of Thailand’s Prime Minister Paetongtarn Shinawatra in 2025. Her successor Anutin Charnvirakul, leader of the Bhumjaithai (Thai Pride) Party, took office that September, dissolved parliament in December and won in a general election the next February, in part by maintaining a hard line on Cambodia amid a wave of Thai nationalism. The episode evoked memories of the 2008 conflict between Cambodia and Thailand, when royalist opponents of Paetongtarn’s father, the controversial former Prime Minister Thaksin Shinawatra, fanned nationalist discontent over the border to undermine the Thaksin-aligned government of the day. Nationalist zeal has also appeared to bolster the government of Prime Minister Hun Manet in Cambodia, though further fighting could shake the unity of the ruling Cambodian People’s Party and the regime built by his father, and current senate president, Hun Sen.

While the ceasefire has held thus far, the conflict continues through diplomatic channels, with Cambodia decrying Thai occupation of its territory.

While the ceasefire has held thus far, the conflict continues through diplomatic channels, with Cambodia decrying Thai occupation of its territory. Thailand insists it is observing the ceasefire agreement, which provides for troops to remain in positions they held when it came into effect, and accuses Cambodia of attempting to internationalise the dispute. Compulsory conciliation on the overlapping maritime claims will take at least a year to conclude. In the meantime, Bangkok has declined to resume the technical work of a Joint Boundary Commission to survey and demarcate the land border between the countries, while cooperation on demining the frontier has been suspended since the 2025 fighting. Both sides are angry, with each portraying the other as the obstacle to resolving the conflict. Amid the mutual recriminations, it would be easy for a minor border incident to blow up into something bigger, including a third bout of major fighting.

Ideally, a third party would mediate between Cambodia and Thailand to head off the possibility of escalation. But several factors impede movement toward dialogue. First, strident nationalism on both sides makes compromise appear hazardous. In Bangkok, the government seems content with the status quo and is following the military’s lead on border security. In Phnom Penh, senior leaders recognise the risks another round of fighting could pose to the government’s legitimacy, but they cannot appear to be bending on sovereignty or territorial integrity. Confrontation continues, for now, to bring political rewards to decision-makers on both sides, especially the Thai military, which has been able to polish a tarnished image.

Secondly, while the conflict has been economically damaging to both countries, it has not been sufficiently costly to precipitate a thaw in the interest of resuming cross-border commerce. Both Thai and Cambodian leaders perceive the political costs of conciliatory moves as greater than the prospective benefits.

Thirdly, international powers have limited leverage to push the two sides toward a deal. Malaysian Prime Minister Anwar Ibrahim, the rotating chair of the Association of South East Asian Nations (ASEAN) in 2025, took the lead in brokering the July ceasefire – with decisive help from Trump’s trade talks threat. But since that truce unravelled, the bloc has been unable to expedite resolution of the dispute. Current ASEAN chair the Philippines has used its good offices to bring the Cambodian and Thai prime ministers together, but it is in no position to spur dialogue. Preoccupied with the Middle East, the U.S. shows no interest in mediating. China would be able to convene talks, but it is unlikely to jeopardise its relations with either country by attempting to impose an agreement.

Under these circumstances, immediate prospects for concerted efforts to resolve the border issue are poor. But until the dispute is resolved, the possibility of another war, with all the associated death, displacement and other human suffering, will remain. Both sides should dial down official rhetoric that casts the other as an enemy and seek areas of common interest, starting by normalising diplomatic relations and reposting ambassadors in the other’s capital. Though the Joint Boundary Commission has neither the mandate nor a mechanism to resolve the political impasse, its work of surveying and demarcating the border is a prerequisite for settling the dispute and should be restarted as soon as possible. Demining is a priority for both countries that should offer another politically acceptable platform for cooperation. Crucially, both border demarcation and demining are already stipulated in the ceasefire agreement. The alternative to honouring these truce terms that the two neighbours have agreed upon could be more bloodshed, which is highly unlikely to put this long-running border dispute to rest.

Bangkok/Phnom Penh/Brussels, 9 October 2026

I. Introduction

The border dispute between Cambodia and Thailand is hardly new, but the fighting that erupted between the two South East Asian neighbours in July and December 2025 was deadlier and more widespread than earlier clashes, killing at least 150 people and displacing roughly one million.1For background, see Crisis Group Asia Report N°215, Waging Peace: ASEAN and the Thai-Cambodian Border Conflict, 6 December 2011; and Matthew Wheeler, “Border Dispute with Cambodia Sparks Political Disarray in Thailand”, Crisis Group Commentary, 1 July 2025. See also “Situation Report 20 – Displacement Crisis as a Result of the Cambodia-Thailand Border Conflict”, World Vision International in Cambodia, 2 January 2026; and “Thai deadly border clashes displace over half a million in Cambodia”, France 24, 21 December 2025. By 27 December, when the parties reached the latest ceasefire, Thai troops had taken high ground in many locations along the 800km border, occupying contested areas as well as patches of Cambodian territory.2Given that portions of the border are undemarcated and disputed, its exact length is not known. Cambodia’s estimate is 817km; Thailand’s is 798km. Since then, the ceasefire has been tested regularly. Bangkok and Phnom Penh have made little progress toward delimiting the border or resuming normal diplomatic relations. The risk of a third round of war is real.

In the wake of the 2025 fighting, bilateral relations are at a low ebb. Each side accuses the other of having started the conflict, while indulging in provocative rhetoric and actions that undermine prospects for resolution. Cambodia alleges that Thailand aims to annex parts of its territory seized in the December 2025 fighting. Thailand maintains that it is observing the ceasefire deal, which stipulates that troops remain in positions they held when the agreement entered into force. The territorial dispute extends out to sea as well. In May, Bangkok withdrew from a 2001 memorandum of understanding on overlapping maritime claims, leading Phnom Penh to initiate compulsory conciliation, a non-binding dispute resolution mechanism under the UN Convention of the Law of the Sea (UNCLOS).

This report examines the roots of the conflict, its domestic political drivers and the current diplomatic impasse. It is based on research conducted since February in Bangkok and Phnom Penh, including interviews with officials of both governments, some of whom have retired but have direct knowledge of developments, as well as diplomats, analysts and journalists covering the conflict. Women made up about a fifth of the interlocutors. Research was also carried out in Siem Reap and Anlong Veng in Cambodia, as well as in the Thai border provinces of Buriram, Sa Kaeo, Si Sa Ket and Surin. The report uses both Khmer and Thai place names on first reference. It uses the Khmer name for the 11th century Preah Vihear temple, known in Thai as Khao Phra Viharn, in view of the 1962 International Court of Justice (ICJ) ruling that the temple is situated in Cambodian territory.3“Case concerning the Temple of Preah Vihear (Cambodia v. Thailand)”, International Court of Justice (ICJ), 15 June 1962.

II. The Weight of History

The contemporary border conflict is a legacy of both colonialism and nationalist historical narratives, which elites in both Cambodia and Thailand have repeatedly exploited for domestic political advantage.

A. Preah Vihear and Thailand’s “Lost Territories”

In the 18th and 19th centuries, Siam and Vietnam vied for control of Cambodia, while Khmer kings sought room for manoeuvre by playing the larger powers against each other.4The Khmer Empire, renowned for building Angkor Wat, dominated mainland South East Asia from roughly the 9th to the 15th century. Siam gained suzerainty over what is now western Cambodia in 1794, but it did not actively colonise the area.5David Chandler, A History of Cambodia (Boulder, Colo., 2008), pp. 142-143; 183-184. France then established a protectorate over Cambodia in 1863, stopping the kingdom’s neighbours from swallowing it whole. In 1893, French gunboats dropped anchor in waters near the royal palace in Bangkok to press Siam to cede territories east of the Mekong River, as well as the eastern provinces of Chantaburi and Trat, to France. This event, known as the Pak Nam Crisis, marks the origin of a still-ubiquitous Thai historical narrative of “lost territories” sacrificed by King Chulalongkorn to preserve his domain from the encroachment of Western colonialism.6Thongchai Winichakul, Siam Mapped: A History of the Geo-Body 0f a Nation (Honolulu, Hawaii, 1994), pp. 111, 150-153; Shane Strate, The Lost Territories: Thailand’s History of National Humiliation (Honolulu, Hawaii, 2015).

Franco-Siamese treaties of 1904 and 1907 established that the border between Siam and French Indochina would follow the watershed of the Dangrek Mountains. In 1908, Siam received a series of maps, drafted by a French expedition, depicting a border line.7The expedition that drafted the map was supposed to be a joint Franco-Siamese endeavour, but Siam did not send surveyors to participate. These maps, known as Annex I of the 1907 treaty, deviate from the treaty’s text; the border line departs from the watershed to place the ancient temple complex of Preah Vihear – a vestige of the Khmer empire – within French Indochina. Siamese officials did not detect the discrepancy until they made their own survey in 1934, but they raised no objection until much later.8Strate, The Lost Territories, op. cit., pp. 161-162. The 1:200,000-scale Annex I border maps remain the only legally recognised ones.

In Thailand, Preah Vihear became a national cause under Field Marshal Phibun Songkhram, a strongman who governed the country from 1938 to 1944 and again from 1948 to 1957. In 1939, the Department of Education included the temple complex on maps of Thailand’s historical sites. During World War II, Thailand reclaimed Cambodia’s western provinces, encompassing the Preah Vihear complex. The Thai government promoted the temple as a symbol of territories earlier surrendered to colonial powers to retain Siam’s independence.9Ibid., pp. 162-163. As a condition for admission to the UN, Thailand then ceded the Cambodian provinces to France under the 1946 Washington Treaty, but it asserted Thai sovereignty over Preah Vihear after Cambodia gained independence in 1953.10Sok Udom Deth, A History of Cambodia-Thailand Diplomatic Relations, 1950-2020 (Glienicke, 2020), p. 26.

In Thailand, press coverage of the [1958] negotiations stirred up nationalist sentiments, helping turn Preah Vihear [temple] into a popular issue.

After years of wrangling, formal bilateral talks about the disputed temple began in 1958. In Thailand, press coverage of the negotiations stirred up nationalist sentiments, helping turn Preah Vihear into a popular issue. Similarly, Cambodia’s King Norodom Sihanouk promoted the historical monument as a national cause, portraying Thailand as a perennial threat to the nation’s sovereignty.11Strate, The Lost Territories, op. cit., pp. 165-166.

Cambodia withdrew from negotiations in October 1959 and appealed to the ICJ to settle the dispute. In 1962, the court ruled that Preah Vihear was situated in Cambodian territory, reasoning that Siam’s failure to object to the Annex I map in the decades after it was issued signified acceptance.12“Case concerning the Temple of Preah Vihear (Cambodia v. Thailand)”, op. cit. In Thailand, the verdict inflamed popular opinion, helping entrench the idea of “lost territories” and national humiliation at the hands of Cambodia and colonial powers.13Strate, The Lost Territories, op. cit., p. 170.

B. Managing a Disputed Border

The Khmer Rouge victory in Cambodia in 1975 opened a new chapter along the border. After Vietnam’s 1978 invasion of Cambodia, almost a million refugees fled to Thailand. Refugee camps became strongholds of armed groups, including the Khmer Rouge, resisting Vietnam’s occupation with Thai, Chinese and U.S. assistance.14Nicole Jenne, “The Thai-Cambodian Border Dispute: An Agency-centred Perspective on the Management of Interstate Conflict”, Contemporary Southeast Asia, vol. 29, n0. 2 (2017), p. 329. In the late 1980s, Thailand reoriented its regional diplomacy, seeking a change from “from battlefield to marketplace”.15Chatchai Choonhavan, Thai prime minister from 1988 to 1991, advanced this policy. Meanwhile, the 1991 Paris Peace Accords and the UN Transitional Authority in Cambodia brought relative peace and the prospect of economic development.

In accordance with these changes, the two countries took steps to establish a new relationship, leading them to sign a bilateral agreement on border management in 1995.16“Agreement between the Government of the Kingdom of Thailand and the Government of the Kingdom of Cambodia on the Establishment of Border Committees”, Phnom Penh, 26 September 1995. This pact set up the General Border Committee (GBC), chaired by the countries’ defence ministers, and three Regional Border Committees (RBC), chaired by regional military commanders charged to “consider and agree on appropriate measures to promote cooperation in the maintenance of peace, order and stability in the border area”.17Ibid. The agreement empowered the RBCs to “solve specific problems that may arise” and promote cooperation and communication links “to enable immediate contact at all times”.18Ibid. The relevant commands are: Thailand’s 2nd Army Region and Cambodia’s 4th Military Region; Thailand’s 1st Army Region and Cambodia’s 5th Military Region; Thailand’s Chanthaburi-Trat Border Defence Command and Cambodia’s 3rd Military Region.

The [Joint Boundary Commission] has ... succeeded in delimiting some 600km of the [Thailand-Cambodia] border, with roughly 200km outstanding.

Five years later, Cambodia and Thailand signed a memorandum of understanding establishing a Joint Boundary Commission (JBC) to govern border surveys and demarcation.19“Memorandum of Understanding between the Government of the Kingdom of Thailand and the Government of the Kingdom of Cambodia on the Survey and Demarcation of Land Boundary”, 14 June 2000. This document – known as MOU 43 for the Buddhist year 2543 in which it was signed – provides for a five-step process, including identifying the 73 boundary markers installed between 1909 and 1919, jointly surveying the boundary and demarcating the border. In 2003, the two sides then agreed on Terms of Reference dividing the border into seven sectors.20“Terms of Reference and Master Plan for the Joint Survey and Demarcation of Land Boundary between the Kingdom of Thailand and the Kingdom of Cambodia”, p. 14. The JBC has since succeeded in delimiting some 600km of the border, with roughly 200km outstanding.21“Thai-Cambodian border row: Does 1:50,000 or 1:200,000 mapping give the edge?”, The Nation, 16 June 2025.

In 2001, Bangkok and Phnom Penh signed a separate memorandum of understanding on overlapping maritime claims. Known as MOU 44, it provided for boundary delineation and joint development of hydrocarbons in a portion of the 26,000 sq km disputed area, which may contain as much as eleven trillion cubic feet of natural gas and between 300 and 500 million barrels of crude oil, with a combined value of some $300 billion.22“Memorandum of Understanding between the Government of the Kingdom of Thailand and the Government of the Kingdom of Cambodia regarding their Overlapping Maritime Claims to the Continental Shelf”, 18 June 2001; Supalak Ganjanakhundee, “Beyond scrapping the MOU: Navigating maritime disputes under UNCLOS”, Prachatai English, 1 June 2026. Appended to the document is a map depicting the two sides’ continental shelf claims and the resulting areas of overlap. This map has spurred criticism in Thailand as the Cambodian claim line appears to cross the island of Koh Kut, which the 1907 treaty had clearly identified as Siamese territory.

C. Politics and Conflict

The historical dispute over territory does not in itself explain why conflict erupted in 2025. Contemporary tension between the two countries is intimately linked to Thailand’s turbulent domestic politics, which for two decades has revolved around a contest for power between the tycoon-turned-politician Thaksin Shinawatra and his conservative opponents.23See Crisis Group Asia Reports N°274, Thailand’s Lengthening Roadmap to Elections, 10 December 2015; N°263, A Coup Ordained? Thailand’s Prospects for Stability, 3 December 2014; and N°192, Bridging Thailand’s Deep Divide, 5 July 2010; as well as Crisis Group Asia Briefings N°121, Thailand: The Calm before Another Storm?, 11 April 2011; N°82, Thailand: Calming the Political Turmoil, 22 September 2008; and N°80, Thailand: Political Turmoil and the Southern Insurgency, 28 August 2008. Thaksin also had close ties with Cambodia’s Hun Sen, who served as prime minister from 1985 to 2023, currently presides over the senate and still controls the ruling Cambodian People’s Party. That relationship crumbled in dramatic fashion in June 2025, with direct repercussions for bilateral relations.

1. Thailand

Thaksin became prime minister in 2001. His Thai Rak Thai Party won support by delivering on popular policies but earned the enmity of conservatives and the military over alleged conflicts of interest and challenges to the prerogatives of the royal palace. Led by conservative royalists, the People’s Alliance for Democracy (PAD) took to the streets to call for Thaksin’s resignation in 2005. The military ousted him in a September 2006 coup, sending him into exile, but his proxy parties continued to win elections. The Thaksin/conservative divide was the fulcrum of Thai politics for more than a decade.

In May 2008, under a Thaksin-aligned government, Thailand signed a joint communiqué with Cambodia supporting inscription of Preah Vihear temple as a UNESCO World Heritage Site. The PAD promptly began using this issue as a cudgel against Thaksin, playing on the memory of the 1962 ICJ decision and the theme of lost territory, and portraying Thaksin’s purported business dealings in Cambodia as a threat to Thai sovereignty.24Crisis Group Report, Waging Peace, op. cit., pp. 4-5. Ever after, despite a lack of hard evidence of any conflict of interest, Thaksin’s opponents would accuse the Shinawatra family of “selling out” the national interest to Hun Sen.25Puangthong Pawakapan, State and Uncivil Society in Thailand at the Temple of Preah Vihear (Singapore, 2013), pp. 37, 62-64.

With Preah Vihear [temple] ... a live political issue in Thailand, tensions increased on the border [with Cambodia].

With Preah Vihear again a live political issue in Thailand, tensions increased on the border. The two sides exchanged fire on six occasions between October 2008 and May 2011, claiming at least 34 lives.26Martin Wagener, “Lessons from Preah Vihear: Thailand, Cambodia and the Nature of Low-Intensity Border Conflicts”, Journal of Current Southeast Asian Affairs, vol. 30, no. 3 (2011), pp. 32-33. In April 2011, Cambodia requested that the ICJ interpret the 1962 verdict, particularly Thailand’s obligation to withdraw troops from the Preah Vihear temple or “its vicinity on Cambodian territory”. In July, the court issued a provisional ruling, including establishment of a demilitarised zone around Preah Vihear. In 2013, the ICJ affirmed Cambodia’s sovereignty over the promontory on which Preah Vihear is situated but referred delineation of the border in adjacent disputed territory to bilateral negotiations. “Request for interpretation of the Judgment of 15 June 1962 in the Case concerning the Temple of Preah Vihear (Cambodia v. Thailand) Request for the indication of provisional measures”, Summary of the Judgment, ICJ, 11 November 2013.

In 2009, in a provocation to his political opponents, Thaksin accepted an appointment as an adviser to Hun Sen, who also offered refuge to his supporters fleeing a 2010 Thai army crackdown. Thaksin’s sister Yingluck, prime minister from 2011 to 2014, then took refuge in Cambodia after the Constitutional Court disqualified her from office, just before the military staged a coup.

With the Thai military firmly in power and both Thaksin and Yingluck in exile, the pro/anti-Thaksin antagonism no longer defined Thai politics. But in 2023, the Thaksin-aligned Pheu Thai Party struck a bargain with its erstwhile conservative foes, joining forces to keep the progressive People’s Party from power after its massive general election victory. The deal allowed Thaksin proxy Srettha Thavisin to become prime minister and Thaksin himself to return home from fifteen years in exile. Hun Sen was Thaksin’s first visitor from abroad.

2. Cambodia

Cambodia is ostensibly in transition from rule by Hun Sen to government by Hun Manet, who replaced his father as prime minister in 2023. During his 38 years as prime minister, Hun Sen consolidated power through a mix of co-optation and repression, while casting himself as Cambodia’s saviour. Beginning in 2017, a crackdown on dissent saw the main opposition party outlawed, scores of politicians jailed and driven into exile, and independent media suppressed.27Lee Morgenbesser, “Cambodia’s Transition to Hegemonic Authoritarianism”, Journal of Democracy, vol. 30, no. 1 (2019); Neil Loughlin, “Beyond Personalism: Elite Politics and Political Families in Cambodia”, Contemporary Southeast Asia, vol. 43, no. 2 (2021); “Cambodia: Hun Sen Extinguishes Media Freedom”, Human Rights Watch, 13 February 2023. Hun Sen remains extremely powerful, both as senate president and as the leading figure in the ruling Cambodian People’s Party (CPP).

Hun Manet’s rise to the prime minister’s office is part of a generational succession designed to secure the Hun family’s pre-eminence by safeguarding the interests of other senior CPP figures; the sons of some of Hun Sen’s long-serving ministers took over their fathers’ posts at the same time.28Tea Banh, defence minister since 1993, handed down his position to his son Tea Seiha and Sar Kheng, interior minister since 1992, turned over his post to his son Sar Sokha. Hun Manet’s younger brothers also ascended to high-ranking positions. Will Brehm, “How did Hun Sen engineer a seamless succession in Cambodia?”, East Asia Forum, 9 September 2023. Unassuming and technocratic, Hun Manet appears focused on governance and economic reforms, but he governs in his father’s shadow, and it remains to be seen if he can keep Hun Sen’s coalition intact.29Crisis Group interview, former official, Phnom Penh, May 2026. See also Chheang Vannarith, “Hun Manet’s Worldview”, Southeast Asian Affairs 2025 (Singapore, 2025).

While domestic political opposition is weak, Hun Sen appears worried about popular discontent.30Crisis Group interviews, diplomats and analysts, Phnom Penh, February 2026. The Hun family’s grip on power is not necessarily secure, as CPP factions weigh a post-Hun Sen future.31Crisis Group interviews, analysts, former official, Phnom Penh, February and May 2026. On 1 June, Hun Sen warned, “Only the ‘angels’ [CPP members] and their children have the right to govern this country”.32“Hun Sen warns extremists against ouster attempts”, Khmer Times, 3 June 2026. While Khmer nationalism has generally been the province of the CPP’s political opponents, confrontation with Thailand has offered Hun Sen an opportunity to burnish his own nationalist credentials and bolster his family’s political legitimacy during the period of generational succession.33Crisis Group interviews, analysts, Phnom Penh, February 2026.

III. The Path to Conflict

A convergence of heightened Thai nationalism, linked to conservatives’ antipathy for Thaksin, and escalatory actions by Cambodia, led to two rounds of fighting in 2025.

A. The Resurgence of Thai Nationalism

The unlikely bargain between Thaksin and conservative parties struck in 2023 to keep the progressive People’s Party from power set the stage for a revival of Thai nationalism anchored in anti-Cambodia sentiment. In February 2024, Prime Minister Srettha Thavisin agreed to open talks with Hun Manet on joint development of hydrocarbons in the maritime overlapping claims area, providing Thaksin’s opponents with a pretext to reopen the 2008 “lost territories” playbook.34“Thailand, Cambodia to discuss joint petroleum exploitation”, Bangkok Post, 7 February 2024. The refrain only grew stronger after Thaksin gave a speech that included a pledge to “unlock” the Gulf of Thailand’s oil and gas resources in August.35William J. Jones, “Thai nationalism rears its ugly head again”, East Asia Forum, 17 January 2025.

Thaksin’s daughter Paetongtarn Shinawatra became prime minister in August 2024 and continued these nascent efforts, stirring the disquiet of conservatives and old PAD networks about MOU 44.36Thailand’s Constitutional Court removed Srettha Thavisin from office on 14 August 2024 for violating ethical standards in a cabinet appointment. Critics of the agreement argued that it jeopardised Thai sovereignty over the island of Koh Kut, conferred structural advantages upon Cambodia and reflected conflicts of interest on the Shinawatra clan’s part.37Tita Sanglee, “Doubt and Dissent: Thai Nationalist Views on the Thailand-Cambodia Maritime Dispute”, ISEAS Perspective, no. 9, 2025, p. 3. As a prominent Thaksin critic asked: “[F]or whose benefit is the Thai government rushing to negotiate within the old framework, given that [MOU 44] contradicts the 1973 Royal Decree [codifying Thailand’s continental shelf claim] and risks territorial loss, as in the Preah Vihear case?”38“‘Mom Korn’ points out that MOU 44 contradicts the royal decree of King Rama IX, risks losing territory and urges its immediate cancellation”, Thai Post, 25 October 2024 [Thai].

In June 2024, Paiboon Nititawan, deputy leader of the military-backed Phalang Pracharat Party (PPRP), petitioned the Constitutional Court to determine whether MOU 44 was illegal because parliament had not approved it.39“PPRP seeks ruling on MoU with Cambodia”, Bangkok Post, 14 June 2024. The court dismissed the petition in September of that year, on the grounds that Paiboon lacked the standing to bring such a case.40“Court verdict empowers Thai government to push energy deal with Cambodia”, Thai PBS World, 17 September 2024. The PPRP then held a press conference a month later alleging that joint development under MOU 44 could jeopardise Thailand’s sovereignty over Koh Kut, putting the government on the defensive.41“Thai territory bordering Cambodia is safe, says government”, Bangkok Post, 31 October 2024. Amid demands from the party and conservative activists to scrap MOU 44, Thailand’s defence minister visited the island to assert Thailand’s sovereignty.42“Thailand cannot scrap MOU 44 without Cambodia’s okay: Anutin”, The Nation, 4 November 2024; “Thai deputy PM makes case for Cambodia deal”, Bangkok Post, 9 November 2024.

B. Border Tensions

With maritime tensions simmering, friction increased along the land border. On 13 February 2025, a group of Cambodians visited the disputed Ta Muan Thom/Tamone Thom temple, reportedly escorted by Cambodian soldiers, and sang a patriotic song. Thai soldiers objected to the implicit assertion of sovereignty, which contradicted the “gentlemen’s agreement” governing the area since 2011, and asked the group to leave.43The arrangement permitted villagers from both nations to visit the temple but prohibited political or nationalist demonstrations. William J. Jones, “Cambodia undermines ASEAN centrality in 2025 border conflict”, Geopolitical Monitor, 29 January 2026. Video of the incident went viral.44“Thai-Cambodian tensions over anthem at temple”, Bangkok Post, 17 February 2025. Two weeks later, on 1 March, a pavilion in the Cambodia-Laos-Thailand tri-border area, built to commemorate neighbourly relations among the three countries, burned down.45“Thailand and Cambodia to discuss pavilion fire”, Bangkok Post, 6 March 2025. While the Thai military officially called it an accident, rumours circulated that Cambodian troops had set off the blaze.46Crisis Group interview, retired senior Thai military officer, Bangkok, June 2026. See also “Thailand and Cambodia to discuss pavilion fire”, op. cit.

The situation escalated on 28 May, when Thai and Cambodian troops exchanged fire in a disputed area between Chong Bok in Thailand’s Ubon Ratchathani province and Cambodia’s Preah Vihear province, killing a Cambodian soldier; both sides claimed the other shot first.47“One killed after Thai and Cambodian soldiers briefly clash in a disputed border area”, Associated Press, 28 May 2025. A week earlier, Thailand had alleged that Cambodian troops had been digging trenches and building fortifications in disputed territory in the area but had agreed to withdraw after talks between local commanders. “Thai, Cambodian troops hold talks over border patrol dispute”, The Nation, 18 May 2025. Prime Minister Paetongtarn spoke to Hun Manet the same day. “We don’t want this to escalate”, she told the media.48“Paetongtarn discusses with Hun Manet after Thai-Cambodian border clash”, The Nation, 29 May 2025. The countries’ army chiefs met two days later and agreed to pull back their troops.49“Army chiefs try to resolve Thai-Cambodian border dispute”, Bangkok Post, 30 May 2025.

A welter of developments ensued in June. On 4 June, more than a week after the clash with Cambodian troops, Paetongtarn’s government released a statement affirming “unwavering commitment to safeguarding sovereignty and territorial integrity”.50“Statement by Thai Government on Thailand-Cambodia Border Situation”, Thai Government Public Relations Department, 4 June 2025; “Thailand, Cambodia mobilise troops, evacuate villages”, The Nation, 5 June 2025. Two days later, Thailand’s National Security Council delegated full authority to military commanders to administer all border crossings; within a day, the army halved the opening hours at Ban Khlong Luek-Poipet, the main checkpoint along the frontier.51“Thailand enforces border controls to safeguard communities amidst rising tensions”, The Nation, 7 June 2025; “Early border closure in Sa Kaeo strands thousands”, Bangkok Post, 7 June 2025. In mid-June, Hun Sen called on Cambodian workers in Thailand – more than 1.5 million people – to come home, while Hun Manet ordered border provinces to prepare for a wave of returnees.52“Hun Sen calls upon Cambodian workers to return home from Thailand, before Thai authorities expel them”, Khmer Times, 14 June 2025; “Cambodia braces for mass deportation, mobilises to welcome workers home”, Cambodianess, 14 June 2025. In 2024, Thailand recorded some 459,863 documented Cambodian workers. Estimates of the total, including undocumented persons, range between one and two million. “Cambodia CTIP and Thailand CTIP”, Winrock International, September 2024, p. 4.

As tensions rose, the two sides convened a meeting of the Joint Boundary Commission – the first since 2012.53“Press conference on the 6th meeting of the Thailand-Cambodia Joint Boundary Commission”, Thai Ministry of Foreign Affairs, 15 June 2025. The JBC affirmed agreement on the position of 45 of 73 boundary markers and revised the 2003 Terms of Reference to incorporate light detection and ranging technology in aerial photographic maps.54Light detection and ranging is a remote sensing method that determines distance by emitting laser pulses at a target and measuring how long the reflected light takes to return to a receiver. Airborne light detection and ranging units can accurately measure and map ground elevation across large areas. Galen Scott, “Lidar: Lasers, Airplanes and Drones!”, The Earth Scientist, vol. 40, no. 3 (2023), pp. 3-4. Experts said it was a breakthrough, because these instruments can quickly produce accurate 3D terrain maps.55William J. Jones and Narut Chareonsri, “The Sovereignty Straitjacket: Cambodia-Thailand Relations, Withdrawal from Memorandum of Understanding 2001 and Regional Security”, Kyoto Review of Southeast Asia, no. 42 (March 2026). Nevertheless, the two sides issued contradictory statements, with Cambodia asserting that the JBC had agreed to use the 1:200,000 scale map annexed to the 1907 treaty, while Thailand’s foreign ministry denied that any such discussion had transpired.56“Cambodia categorically refuses to recognize the map drawn unilaterally by Thailand as a basis for border issues”, Khmer Times, 15 June 2025; “Tension lingers following Thailand-Cambodia JBC talks”, Prachatai English, 17 June 2025. On 15 June, Cambodia formally petitioned the ICJ to determine the sovereignty over four disputed sites, three of which encompass Khmer Empire-era temple ruins that nationalists on both sides have imbued with cultural and political significance.57The sites are Ta Moan Thom, Ta Moan Tauch, Ta Krabei temple and Mom Bei/Chong Bok. “Cambodia turns to World Court over Thailand border disputes”, Reuters, 15 June 2025. Two weeks earlier, Hun Manet raised the possibility of Cambodia and Thailand seeking a joint ICJ referral, but Bangkok rejected it, having withdrawn recognition of the court’s compulsory jurisdiction in 1960. “Hun Manet calls for urgent border talks with Thailand, proposes ICJ resolution for disputed areas”, Khmer Times, 2 June 2025; “Thailand urges positive engagement after Cambodia threatens to take dispute to World Court”, Reuters, 5 June 2025. The move antagonised Bangkok, which has long maintained that the dispute should be settled bilaterally.58“Thailand’s position in response to Cambodia’s submission on 15 June 2025 of a letter to the International Court of Justice related to the Emerald Triangle (Mom Bei), Ta Moan Thom, Ta Moan Tauch and Ta Krabei temples”, Thai Ministry of Foreign Affairs, 16 June 2025.

C. The Fateful Telephone Call

On 15 June, Prime Minister Paetongtarn had a telephone conversation with Hun Sen, a nine-minute recorded excerpt of which was made public three days later.59Hun Sen acknowledged that he had recorded the call and shared it with some 80 party officials, suggesting that one of them leaked the audio. He later released the full seventeen minutes on his Facebook page. “Hun Sen admits to recording phone call with Thai PM and sharing with 80 officials”, The Nation, 18 June 2025; “Cambodian-Thai tensions escalate on diplomatic and economic fronts”, Khmer Times, 23 June 2025. It revealed that, in her efforts to de-escalate, she was deferential to Hun Sen, addressing him as “uncle” and seeking his understanding regarding the precarious political situation the border dispute had created for her government. Most damagingly, she described the 2nd Army Area commander, Lieutenant General Boonsin Padklang, who was in charge of the areas where clashes had occurred, as belonging to “the opposite side”, a reference to the Thaksin/conservative divide. For his part, Hun Sen asked her to prevail on the Thai military to reopen the border.60Nattan Casey Plewissara, “The leaked call shaking Thai politics: Translated”, The Asia Cable (blog), 22 June 2025.

The leaked audio roiled Thai politics, confirming the open secret of dissension between government and military, already exacerbated by popular perceptions that the Pheu Thai-led government had been slow in dealing with Cambodia. In contrast, the military, and especially Boonsin, gained public support for adopting an uncompromising stance.61“A general at ease: Lt Gen Boonsin’s quiet weekends amid Thai-Cambodian tensions”, Bangkok Post, 14 June 2025. As an analyst put it, the government’s response “accidentally [made] Thai nationalism cool again”.62Ken Lohatepanont, “Thai government fails to meet the nationalist moment”, The Coffee Parliament (blog), 8 June 2025.

For Thaksin’s critics, the telephone call also appeared to confirm longstanding suspicions that the Shinawatra clan was ready to collude with Hun Sen and “sell out” the country for personal gain.63Susannah Patton, “A border skirmish and leaked phone call sees the Thailand-Cambodia dispute surge back to life”, The Interpreter, 20 June 2025; “Thai protesters vent their exasperation with the prime minister”, The New York Times, 28 June 2025. In their view, the call also showed Paetongtarn – Thailand’s youngest-ever prime minister – to be out of her depth in a crisis and thus ripe for unseating.64Crisis Group interviews, officials and journalists, Bangkok, April and June 2026.

The political consequences unfolded rapidly. The day the recording was exposed, Deputy Prime Minister Anutin Charnvirakul pulled his Bhumjaithai Party out of the coalition government and called on Paetongtarn to take responsibility for harming the nation’s honour.65“Bhumjaithai party announces withdrawal from government coalition”, The Nation, 18 June 2025. The Constitutional Court suspended her from office on 1 July while it considered a petition submitted by 36 senators that she had breached constitutional ethical standards.66Deputy Prime Minister Phumtham Wechaiyachai became acting prime minister. “July legal battles fuel momentum for political reset”, Bangkok Post, 25 June 2025; “Constitutional Court suspends Paetongtarn as PM because of Hun Sen’s clip”, The Nation, 1 July 2025.

The Pheu Thai Party-led government ... adopted a firmer stance toward Cambodia, highlighting its role as a hub of transnational crime.

The leaked audio also had bilateral repercussions, strengthening the Thai military’s hand.67Paul Chambers, “The 2025 Thai-Cambodian Conflict from Thailand’s Perspective”, Asia Policy, vol. 21, no. 2 (April 2026), pp. 18-19. On 23 June, the army spokesman announced the closure of all border checkpoints.68“Military seals border with Cambodia”, Bangkok Post, 24 June 2025. The Pheu Thai Party-led government also adopted a firmer stance toward Cambodia, highlighting its role as a hub of transnational crime, particularly industrial-scale fraud in scam compounds.69“Thai PM seeks international crackdown on Cambodia-based scams”, Bangkok Post, 23 June 2025.

On his own social media accounts, meanwhile, Hun Sen kept up a steady stream of invective directed at Thaksin. He spoke of betrayal by the Shinawatras, recalling his hospitality to Thaksin, Thaksin’s sister Yingluck and their supporters; he also predicted that Thailand would have a new prime minister within three months.70“Hun Sen: ‘I predict that Thailand will have a new prime minister within the next three months, and I already know who it will be’”, Khmer Times, 25 June 2025. Why Hun Sen severed his longstanding relationship with Thaksin in this way remains a matter of speculation, but analysts in Phnom Penh attribute it to unhappiness that Thaksin had not delivered on joint development of maritime hydrocarbon deposits.71Crisis Group interviews, analysts and academics, Phnom Penh, February 2026. See also Gregory V. Raymond, “Patronage Networks, Personal Relationships and the Return of the Thai-Cambodia Border Conflict: A Nontraditional Account”, Asia Policy, vol. 21, no. 2 (April 2026). Others point to Paetongtarn’s plans to legalise gambling in Thailand, which would undercut Cambodia’s casinos, or the intensifying Thai campaign against scam centres across the border, which by one rough estimate generate one quarter to two fifths of Cambodia’s GDP.72Crisis Group interviews, analyst, Phnom Penh, February 2026; former government official, Phnom Penh, February 2026. The GDP share estimate appears in Jacob Sims and Bopha Phorn, “The Scam Economy in Cambodia”, Southeast Asian Affairs, 2026, p. 78. Many in Cambodia also believe it was an emotional decision, as Hun Sen was irritated by Paetongtarn calling Hun Manet “unprofessional” for issuing statements on social media.73Crisis Group interviews, former official, academic, Phnom Penh, February 2026; Western diplomat, Phnom Penh, May 2026.

Thailand’s Constitutional Court removed Paetongtarn from office on 29 August, as it had done with all five Thaksin-aligned prime ministers since the 2006 coup.74On 9 September 2025, the Supreme Court sentenced Thaksin to serve the prison term he had avoided upon returning from exile in 2023. He was released the following 11 May. Anutin was elected prime minister a week later, promising fresh elections within four months.75Anutin dissolved parliament on 12 December 2025, and the general election took place on 8 February.

IV. Fighting and Ceasefires

The balance of power between Cambodia and Thailand is lopsided. Thailand dwarfs its neighbour in population (roughly 70 million to 17 million), gross domestic product ($577 billion to $51.2 billion in 2025), military spending ($5.7 billion to $1.3 billion in 2024) and armed forces (360,850 active personnel to 124,300).76World Bank data; “The Military Balance 2025”, International Institute for Strategic Studies, pp. 238; 302-303. These asymmetries weighed heavily on the battlefield, especially during the protracted December fighting in which Thailand gained the upper hand.

A. Round One

Tensions rose sharply after landmines wounded eight Thai soldiers on 16 and 23 July 2025 on the border area of Nam Yeun district, Ubon Ratchathani province.77“Landmine dispute escalates tensions between Thailand and Cambodia”, Reuters, 22 July 2025; “New mine blast inflames border tensions”, Bangkok Post, 23 July 2025. Thailand said the mines were newly laid; Cambodia said they were remnants of earlier conflicts.78Cambodia is among the countries most affected by landmines and other explosive remnants of war, with an estimated contaminated area of 1,856 sq km as of January 2024. See the Cambodian Mine Action Centre website. Thailand then expelled Cambodia’s ambassador and withdrew its own.

On 24 July, fighting broke out between ground troops near Ta Muen Thom and Ta Krabei temples, between Thailand’s Surin and Cambodia’s Oddar Meanchey provinces, with each side accusing the other of firing the first shot.79“Thailand launches airstrikes on Cambodia as border clash escalates”, Washington Post, 24 July 2025. The combat escalated quickly to unprecedented levels. Cambodian BM-21 rockets hit civilian areas in Thailand’s Kantharalak district, killing seven people, including two children, at a petrol station some 20km from the border.80“Strikes on civilians a ‘war crime’”, Bangkok Post, 25 July 2025. Thailand launched airstrikes on military targets in Preah Vihear, the first use of airpower across the Thai-Cambodian border since the early 1970s.81“Thailand and Cambodia exchange fire in new border clashes that kill at least 1 civilian”, Associated Press, 24 July 2025. Altogether, in five days, the exchanges killed at least 48 people and displaced some 300,000 civilians.82“Thailand-Cambodia border calm as military commanders hold talks”, Reuters, 29 July 2025; “Thai police fire tear gas at Cambodian protesters at a disputed border village”, Reuters, 18 September 2025.

On 24 July, Malaysian Prime Minister and acting ASEAN chairman Anwar Ibrahim appealed for a ceasefire.83“Thailand, Cambodia must ‘stand down’ over border clash: Malaysian PM”, Thai PBS World, 24 July 2025. China also pushed for negotiations. Phnom Penh was ready for dialogue, but Bangkok was reluctant until the U.S. also weighed in. President Donald Trump stated that if the two countries did not negotiate, he would suspend trade talks with both. As Thailand was eager to use these talks to secure lower tariffs on exports to the U.S., Trump’s threat was sufficient to bring it to the table with Cambodia.84“Exclusive: Trump’s call broke deadlock in Thailand-Cambodia border crisis”, Reuters, 31 July 2025. On 28 July, acting Prime Minister Phumtham Wechaiyachai met Hun Manet in Putrajaya and agreed to a ceasefire, as well as a meeting of regional military commanders the next day and a meeting of the General Border Committee in early August.85“Joint Press Release on the Special Meeting Hosted by Malaysia to Address the Current Situation between Cambodia and Thailand”, Malaysian Ministry of Foreign Affairs, 28 July 2025. The prime ministers also agreed to Anwar’s proposal for ASEAN observers to monitor the ceasefire.86Crisis Group interview, retired senior military officer, Bangkok, June 2026. See also “ASEAN chair deploys observer team to monitor Thai-Cambodian ceasefire”, The Nation, 28 July 2025.

B. Interregnum

The ceasefire was fragile from the start, with allegations of violations soon emerging from both capitals.

1. Developments on the border

The situation was particularly fraught at Ban Nong Chan and Ban Nong Ya Kaeo in Khok Sung district, Sa Kaeo province abutting Cambodia's Chouk Chey and Prey Chan villages, where thousands of Cambodians had settled as refugees in the 1980s, on land Thailand claims. The Thai military, reportedly impatient with the government’s failure to evict these people, pressed it to act.87“Thai military increases pressure on govt, Cambodia to relocate encroachers”, The Nation, 2 September 2025. Thai riot police scuffled with Cambodians at Ban Nong Ya Kaeo on 17 September, injuring 23 with tear gas and rubber bullets; Thai officers also reportedly sustained injuries.88“Thailand gives Cambodia 30 days to withdraw after border clashes”, Khaosod English, 17 September 2025; “Thai police fire tear gas at Cambodian protesters at a disputed border village”, Reuters, 18 September 2025. In early October, Thailand began stacking up shipping containers to build walls, cordoning off parts of Ban Nong Chan to prevent Cambodians from entering.89“Cargo containers arrive in Ban Nong Chan to reinforce border wall”, Thai PBS World, 10 October 2025.

Amid these confrontations, bilateral border mechanisms kept functioning. On 27 August, a Regional Border Committee meeting affirmed the ceasefire and pledged cooperation on demining and crime suppression.90“Second Army outlines 11-point RBC, Cambodia defers demining and scams to GBC”, The Nation, 27 August 2025. On 10 September, at a special General Border Committee meeting convened in Koh Kong, Cambodia, the parties agreed to remove heavy weapons from the border, develop terms of reference for ASEAN Observer Teams on each side of the border and cooperate on demining. They also said they would refer the matter of Chouk Chey/Nong Chan to the next JBC meeting as a priority for joint survey and demarcation, “peacefully manag[ing] the situation on the ground” in the meantime.91“Joint Press Statement of the Special General Border Committee Meeting, Koh Kong, Cambodia”, Thai Ministry of Foreign Affairs, 10 September 2025.

Despite the positive tone, tensions lingered, as Thai conservative activists whipped up nationalist sentiment. On 10 October, with the Thai military’s permission, social media celebrity Kanthat Pongpaiboonwet began broadcasting piercing, “ghostly” noises through loudspeakers at Ban Nong Chan and Ban Nong Ya Kaeo to intimidate Cambodians.92“Thai army defends psych-ops along Cambodian border”, Bangkok Post, 12 October 2025. Earlier, in late August, Kanthat had brought fourteen sewage trucks to Ban Nong Chan. He had intended to spray protesting Cambodians with sewage, but authorities prevented him from doing so. “Thai social media star stages sewage stunt at tense border”, Bangkok Post, 28 August 2025. The Thai military put a stop to the stunt after a week, but prominent figures who spoke out against it had to seek police protection after receiving death threats.93“Army orders halt to ‘sound war’ against Cambodians in Sa Kaeo province”, Thai PBS World, 19 October 2025; “Action urged after border comment death threats”, Bangkok Post, 21 October 2025.

2. International peace efforts

Meanwhile, in an 8 October letter, President Trump urged Thailand’s new prime minister, Anutin Charnvirakul, to reach a peace deal with Cambodia.94“Thailand snubs Trump’s mediation, tells Cambodia to remove border troops”, Bloomberg, 9 October 2025. Trump agreed to attend the forthcoming ASEAN summit on the condition that he could preside over a peace accord signing ceremony.95“Trump seeks peace ceremony spotlight at ASEAN summit”, Politico, 6 October 2025. Anutin responded that Trump should press Cambodia to meet four conditions: withdrawing heavy weapons, removing landmines, eliminating scam centres and relocating Cambodian settlements on Thai territory.96“Anutin to notify Trump, urging Cambodia to comply with Thai conditions”, The Nation, 9 October 2025.

As the ASEAN summit approached, Thai officials suggested that peace prospects hinged on a JBC meeting and the second Special GBC meeting, both scheduled for 20-23 October.97“Anutin chairs security meeting ahead of GBC-JBC talks”, The Nation, 20 October 2025. These achieved a measure of success: the JBC assented to expediting the joint survey in the Chouk Chey-Nong Chan and Prey Chan-Nong Ya Kaeo area, while the GBC delegations produced an in-principle agreement to withdraw heavy weapons, clear mines and cooperate against scam centres.98“Border talks agree to repair markers, review land holdings”, Bangkok Post, 23 October 2025.

On 26 October, Trump presided over the signing of a joint declaration by Prime Ministers Anutin and Hun Manet, endorsed by Malaysia’s Anwar Ibrahim, on the sidelines of the ASEAN summit in Kuala Lumpur. Despite the fanfare, the joint declaration amounted to a recommitment to the terms of the 28 July ceasefire: withdrawing heavy weapons, coordinating demining and border demarcation, and desisting from dissemination of false information and “harmful rhetoric”.99Thailand also committed to promptly release eighteen Cambodian prisoners of war. “Joint Declaration by the Prime Minister of the Kingdom of Cambodia and the Prime Minister of the Kingdom of Thailand on the outcomes of their meeting in Kuala Lumpur, Malaysia”, White House, 26 October 2025. Speaking at the summit, Anutin sought to reassure the Thai public, saying the agreement would not put Thailand at a disadvantage. He specified that the 1:200,000 map was not discussed and that light detection and ranging technology had rendered the Annex I map obsolete.100“PM claims joint declaration with Cambodia won’t disadvantage Thailand”, Thai PBS World, 26 October 2025.

C. Round Two

Just two weeks after the Kuala Lumpur accord, the ceasefire began to unravel. On 10 November, Prime Minister Anutin said Thailand would stop observing the joint statement after a landmine wounded four Thai soldiers in Kantharalak district.101“Anutin halts Thai-Cambodian peace declaration after Thai troops hit landmine again”, The Nation, 10 November 2025. The four incidents that wounded sixteen Thai soldiers in 2025 all involved recently laid PMN-2 antipersonnel mines, of which Cambodia has stocks. All the incidents occurred on customary patrol routes in contested territory previously known to be safe and often used by both armies. According to an independent analysis, “these incidents [have] the appearance of a targeted military activity”. “Investigation into New Use of Antipersonnel Landmines on the Thai-Cambodia Border”, Landmine Monitor, 1 March 2026, p. 20. On file with Crisis Group. The U.S. briefly tried to intercede, saying it would suspend talks about a reciprocal trade framework agreement – which would have meant higher tariffs – if Bangkok did not reverse course.102“US halts trade talks with Thailand over peace pact compliance”, Bangkok Post, 15 November 2025. But Thai officials learned that no such penalty was forthcoming. Within a month, troops exchanged fire in the same district, and fighting soon spread.103“Thai-Cambodia border clash injures two Thai troops, triggers evacuation”, Khaosod English, 7 December 2025; “Briefing to the Diplomatic Corps and International Organizations on Developments on the Thailand-Cambodia Border Situation”, Thai Ministry of Foreign Affairs, 8 December 2025.

Thai officials made clear that this round of combat would differ from the first. “The aim of the Thai army is to disable Cambodia’s military capability for a long time, for the sake of our children’s safety”, army chief of staff Chaiyapruek Duangprapat explained.104“PM Anutin says no more negotiations with Cambodia”, Thai PBS World, 8 December 2025. On 9 December, Anutin said Thailand was determined to push ahead, notwithstanding calls for dialogue: “We can’t stop now. We’ve already given our commitment to the armed forces that they can fully carry out the planned operations”.105“Border battle expands as Thailand and Cambodia clash for second day”, Reuters, 9 December 2025.

At its height, the fighting had displaced over 600,000 people in Cambodia and some 400,000 in Thailand.

Combat continued for twenty days, including rocket and artillery exchanges and Thai airstrikes that hit targets deep inside Cambodia.106“Cambodia counts the cost of its border war with Thailand”, BBC, 19 December 2025. At its height, the fighting had displaced over 600,000 people in Cambodia and some 400,000 in Thailand.107Roughly 84.5 per cent of the displaced in Cambodia were women and children. “Situation Report 20 – Displacement Crisis as a Result of the Cambodia-Thailand Border Conflict”, op. cit. At least 101 people were killed, including 26 Thai soldiers. Cambodia did not release military casualty figures, but media estimates put the toll at roughly 130 killed.108“Cambodian deaths exceed 110 in December border conflict with Thailand”, Nikkei Asia, 13 January 2026. Reported Thai military estimates of the number of Cambodian troops killed range from 200 to 500. “Army places district out of bounds”, Bangkok Post, 16 December 2025; “Thailand carries out more airstrikes on Cambodia as deadly border conflict flares”, Associated Press, 18 December 2025.

Again, Malaysia’s Prime Minister Anwar played an important role in ending the hostilities.109“Anwar calls Thai, Cambodian leaders to discuss border clashes”, Thai PBS World, 10 December 2025. As ASEAN chairman, he convened a special foreign ministers’ meeting that called for an immediate ceasefire, withdrawal of troops under the watch of interim ASEAN Observer Teams and bilateral dialogue.110“ASEAN Chair’s Statement Special ASEAN Foreign Ministers’ Meeting on the Current Situation between Cambodia and Thailand”, 22 December 2025. Washington urged talks, but Thailand was less inclined to respond to U.S. pressure than it had been in July, as the Trump administration had not imposed the higher tariffs it threatened after Bangkok stopped observing the ceasefire in November.111“On Fighting on the Cambodia-Thailand Border”, press statement, U.S. State Department, 9 December 2025; “Thailand says US trade talks to proceed despite Cambodia dispute”, Reuters, 15 November 2025. China, meanwhile, played a more prominent mediating role in December.112Immediately after the first ceasefire agreement, China’s vice minister for foreign affairs, Sun Weidong, hosted Cambodian and Thai officials for an “informal consultation” in Shanghai. “China vows to continue Thailand-Cambodia peace efforts after ‘informal’ post-truce talks”, South China Morning Post, 30 July 2025. Foreign Minister Wang Yi called his Cambodian and Thai counterparts directly, and Deng Xijun, Beijing’s special envoy for Asian affairs, visited both countries.113“Special Envoy for Asian Affairs of the Ministry of Foreign Affairs Makes Another Shuttle-Diplomacy Trip for Peace between Cambodia and Thailand”, Chinese Foreign Ministry, 25 December 2025.

Cambodia and Thailand eventually agreed to a ceasefire at a special GBC meeting on 27 December. Key provisions include commitments to resume “at the earliest” efforts to survey and demarcate the border using the JBC’s existing mechanisms, as well as to refrain from building up forces along the border.114The two parties also agreed to cooperate against scam centres. “Joint Statement of the 3rd Special General Border Committee between the Kingdom of Thailand and the Kingdom of Cambodia at Ban Pak Kard (Chanthaburi Province of Thailand)-Prum (Pailin Province of Cambodia) International Point of Entry”, 27 December 2025. The day after the agreement was signed, Wang Yi hosted Foreign Ministers Sihasak Phuangketkeow and Prak Sokhonn in Yuxi, Yunnan province.115“Foreign Ministers of China, Cambodia, and Thailand Hold Trilateral Meeting”, Chinese Foreign Ministry, 29 December 2025. According to a Thai official, China played a constructive role outside the media glare: “They are fair, not trying to impose a solution”.116Crisis Group interview, senior official, Thai Foreign Ministry, Bangkok, April 2026.

V. Not Turning the Page

Following the December ceasefire, relations have remained tense with little movement toward restoring normal diplomatic relations or delimiting the land border. Instead, the two governments have remained locked in a contest for international public opinion amid regular border provocations and fears of a third round of war.

A. A New Status Quo

When the dust settled from the December fighting, the Thai military had most of the high ground. Thailand now holds not only territory in contested areas, but also land that is indisputably Cambodian, beyond Bangkok’s proposed border line. Bangkok justifies its action by arguing that the ceasefire froze the conflict where it stood on 27 December, citing point 2 of the joint statement, which says, “Both sides agree to maintain current troop deployments without further movement”.117“Joint Statement of the 3rd Special GBC”, op. cit.

Following the same logic, Thai troops have built walls of stacked shipping containers and barbed wire in disputed areas, notably those from which they forcibly repatriated Cambodian refugees who had settled there in the 1980s.118The areas in question are Ban Nong Chan/Chouk Chey and Nong Ya Kaeo/Prey Chan, in Thailand’s Khok Sung district, Sa Kaeo province and Cambodia’s O’Chrov district, Banteay Meanchey province. Thailand has also built container walls in Bang Tha Sen, Muang district, Trat province/Thma [Thmor] Da, Pursat province; and Chong An Mah, Ubon Ratchathani/An Seh village, Choam Ksan district, Preah Vihear province. According to Cambodian officials, Thailand expelled 1,200 families from these areas.119“A tale of two villages: Cambodians lament Thailand’s border gains”, Agence France-Presse, 7 February 2026. The Thai military, which has also destroyed homes in these locations, describes the barriers as a “reorganisation” needed for security, strictly in accordance with the 27 December joint statement.120“Cambodia says Thai troops still occupy civilian areas, testing December truce”, Reuters, 14 January 2026; “Army denies blocking return of displaced”, Bangkok Post, 29 March 2026. An independent non-governmental organisation in Cambodia determined that Thailand’s destruction of Cambodian homes in disputed areas of Ban Nong Chan/Chouk Chey and Nong Ya Kaeo/Prey Chan may violate international law. “Post-ceasefire Razing of Cambodian Villages Likely Violates International Law”, LICADHO, 20 January 2026. In January, Thai Defence Minister Natthaphon Narkphanit said Thai soldiers would stay deployed along the border for at least a year, adding that veterans may be allowed to settle in formerly restricted zones.121“Troops to man border for ‘at least one year’”, Bangkok Post, 11 January 2026.

Many in Cambodia worry that Thailand is moving toward de facto annexation of the disputed areas and Cambodian territory it currently controls.

Cambodia has objected to this new status quo. On 2 January, less than a week after the ceasefire, its foreign ministry issued a statement identifying fourteen areas held by Thai troops that are “unequivocally within Cambodian territory”, accusing Thailand of “intensifying demolition of Cambodian civilian and cultural structures”, and condemning “an unlawful and continuing occupation … brought about and sustained through the threat and use of force”.122“Statement of the Ministry of Foreign Affairs and International Cooperation, Cambodia’s Protest against Thai Violations”, 2 January 2026. The statement specified the following areas: In Banteay Meanchey province, Prey Chan, Chouk Chey and Boeung Trakuon; in Pursat province, Phluk Domei and Thmor Da International Point of Entry (Chrok Chey Chomneas); in Preah Vihear province, An Ses, Ta Thav and Phnom Trap; and in Oddar Meanchey, O’Smach, K’nar Temple, Ta Krabei temple, Tamone Thom temple, Chob Angkhun and Chok Krous. It is not clear how much Cambodian territory Thailand holds, but it likely amounts to several square kilometres. The Banteay Meanchey governor said Thai troops held 7.6 sq km of territory in Prey Chan, Chouk Chey and Boeung Trakuon. “Thai forces illegally occupying nearly 800 hectares of Cambodian territory in Banteay Meanchey, says governor”, Khmer Times, 24 February 2026. This estimate may include disputed areas, however. Crisis Group interview, Western analyst, Phnom Penh, May 2026. Many in Cambodia worry that Thailand is moving toward de facto annexation of the disputed areas and Cambodian territory it currently controls.123Crisis Group interviews, analysts and government officials, Phnom Penh, February and May 2026. See also “Cambodia doubles down on bid to spotlight Thai occupation”, Khmer Times, 25 February 2026. Phnom Penh organises regular visits by the ASEAN Observer Team and foreign dignitaries to these areas. See, for example, “Cambodia doubles down on legal efforts to counter Thai military encroachment”, Phnom Penh Post, 27 March 2026. Bangkok denies such accusations. But the government has repeatedly organised media trips to a casino resort it seized in the Cambodian border town of O’Smach, which it presents as evidence of Cambodia’s role in permitting scam operations to flourish, prompting Phnom Penh to accuse Thailand of seeking to justify its continued occupation of the site.124“Cambodian scam compound yields trove of fraud evidence, Thai military says”, Reuters, 2 February 2026; “Thailand exposes scam city in O’Smach, invites international scrutiny”, Khaosod English, 7 April 2026; “Cambodia: Thai military’s border media stunt is ‘direct breach’ of UN Charter”, Agence Khmer Presse, 30 June 2026; “Thailand shows observers alleged O’Smach scam and military sites”, The Nation, 8 September 2026.

On 8 February, the Thai general election gave a convincing victory to the Bhumjaithai party, previously the third largest in parliament, led by caretaker prime minister Anutin Charnvirakul. The party positioned itself as a reliable ally of the conservative establishment and pledged a hard line on Cambodia.125The Bhumjaithai party won 191 seats in the 500-seat lower house, the progressive People’s Party 120 seats and Pheu Thai 74. Bhumjaithai formed a coalition with Pheu Thai and fourteen other parties. “Thai poll body certifies election results, clearing path for new parliament”, Reuters, 4 March 2026.

Faced with December’s military setbacks and loss of territory, the Cambodian government took steps to bolster its international standing and domestic legitimacy. Authorities intensified a rolling nationwide crackdown on scam centres, with a senior official declaring on 27 August that large-scale operations had been “brought fully under control”.126“Cambodia declares ‘large scam compounds’ eliminated as criminal networks shift into homes, cafés”, Phnom Penh Post, 29 August 2026. The large compounds have closed, but the crackdown has targeted the premises, not the landlords, officials and financiers who run the scams, so the industry is dispersing into smaller, hidden locations rather than disappearing. Crisis Group interviews, analysts, diplomats and researchers, Phnom Penh, February-September 2026; Crisis Group observations, Sihanoukville and border casino towns, July-August 2026. In May, former opposition leader Kem Sokha, convicted of treason in 2023, received a royal pardon. His daughter, Kem Monovithya, accepted an appointment in August as a special envoy in Hun Manet’s government, specialising in border affairs and trade.127“Kem Monovithya’s new role raises questions over political reconciliation and opposition’s future”, Cambodianess, 19 August 2026.

B. The Diplomatic Impasse

Since the 27 December ceasefire agreement, Phnom Penh has pushed for resuming talks under the JBC, which last convened on 22 October 2025, after the first round of fighting.128“Thai minister sees ‘progress’ toward Cambodia peace deal”, Bangkok Post, 23 October 2025. Between January and April, it made three separate requests for the body to hold a special meeting, but Bangkok demurred each time.129Bangkok first cited the coming general election, then the formation of a new cabinet and finally the need to appoint a new chief delegate to the commission. “Foreign ministry decries Thai efforts to stall JBC demarcation work”, Phnom Penh Post, 13 March 2026; “Thailand not ready for border talks with Cambodia: Sihasak”, Bangkok Post, 12 April 2026.

On 12 April, Hun Manet announced that Cambodia would focus on direct talks to resolve disputes with Thailand.130“Cambodia shifts border resolution priorities: ‘From ICJ to bilateral negotiations’”, Phnom Penh Post, 12 April 2026. It amounted to a concession, given Thailand’s longstanding insistence on resolving differences bilaterally, and a tacit admission that Cambodia’s ICJ gambit in June 2025 was futile, given that Bangkok does not consent to the court’s jurisdiction. Hun Manet said bilateral talks would be faster, but the change in tack likely also reflected a recognition that another round of fighting could threaten his government’s legitimacy.131Crisis Group interview, analyst, Phnom Penh, May 2026.

In another glimmer of potential progress, the two countries’ foreign ministers met on the sidelines of the ASEAN-EU ministerial meeting in Brunei on 27 April, where they discussed border issues among other subjects.132“Cambodian, Thai FMs discuss border issue in Brunei”, Xinhua, 28 April 2026; “Cambodia, Thailand reaffirm ceasefire as rights groups decry arrests over border dispute”, CamboJA News, 28 April 2026. Anutin and Hun Manet then met at the ASEAN summit in Cebu, the Philippines, where they tasked their foreign ministers with developing confidence-building measures.133“Deputy Prime Minister and Minister of Foreign Affairs Attends the Trilateral Meeting between the Leaders of Thailand, the Philippines and Cambodia on the Sidelines of the 48th ASEAN Summit in Cebu, the Republic of the Philippines”, press release, Thai Ministry of Foreign Affairs, 7 May 2026.

[Thailand and Cambodia] have fallen into a pattern of recriminations, with each side attempting to load responsibility for the stalemate on the other.

These minimal efforts at improving relations have not been fruitful, however. Instead, the two countries have fallen into a pattern of recriminations, with each side attempting to load responsibility for the stalemate on the other. Phnom Penh has sought to focus international attention on what it calls Thailand’s illegal actions along the border. It has lodged dozens of formal protests, and senior officials have pointed to what they call violations of sovereignty and efforts to establish a new border line by force.134Between the 27 December ceasefire and 22 June, Cambodia’s JBC delegation lodged nine diplomatic notes with its Thai counterpart and issued 32 formal protest notes about Thai activities. “Cambodia’s JBC sent nine diplomatic notes to Thailand, lodged 32 protests over alleged illegal activities: government spokesperson”, Agence Kampuchea Presse, 22 June 2026. “PM takes Thai border dispute to global parliamentary stage, warns of ‘fait accompli’ attempts”, Phnom Penh Post, 27 August 2026; “Hun Sen declares Thais used ‘scam excuse’ to invade Cambodia, warns of ‘collapse of world order’”, Phnom Penh Post, 27 August 2026.

In response to these protests, Bangkok has said it is in compliance with existing bilateral agreements and international law, while characterising Phnom Penh’s rhetoric as an impediment to resolving the border issue.135“JIC warns threats to arrest Anutin and use force could harm talks”, The Nation, 27 August 2026. Foreign Minister Sihasak has publicly warned Cambodia not to criticise Thailand at international forums and repeatedly called for it to demonstrate sincerity, portraying its diplomatic manoeuvres as efforts to “internationalise the conflict and undermine prospects for peace”.136“Sihasak warns Cambodia against raising bilateral disputes at UNSC”, The Nation, 24 May 2026; “Land border ‘priority’, FM says”, Bangkok Post, 27 April 2026; “Thailand rejects Cambodia’s claims at UN”, Bangkok Post, 25 February 2026. In late August, Sihasak explained Thailand’s rationale for not convening the JBC, arguing that progress on border security, including cooperation on demining and combating criminal networks, must precede survey work and demarcation.137Sihasak Phuangketkeow, “Setting the stage for border talks”, Bangkok Post, 31 August 2026. More recently, the foreign minister denounced Cambodia for “playing the role of a victim with a sense of self-righteousness aimed at claiming the moral high ground”.138“Thailand’s statement at the first meeting of UNCLOS Conciliation Commission”, 15 September 2026.

Bangkok’s reaction to the visit to Cambodia by a UN special rapporteur on human rights, Tom Andrews, exemplifies its defensive stance. Andrews issued an end-of-mission statement on 31 July noting that roughly 650,000 Cambodian civilians had been displaced by the border fighting and more than 20,000 remain unable to return to their homes, as well as highlighting the plight of some 900,000 Cambodian migrant workers who have returned from Thailand.139“Tom Andrews, UN Special Rapporteur on the situation of human rights in Cambodia, End of Mission Statement, 31 July 2026, Phnom Penh, Cambodia”, 3 August 2026. Bangkok swiftly objected to the statement, saying the number of displaced included refugees from the 1970s who had “encroached on Thai territory”, adding that Thailand did not compel the workers to leave.140“Statement: Regarding the Statement by Mr. Tom Andrews, the United Nations Special Rapporteur on the Situation of Human Rights in Cambodia”, Thai Ministry of Foreign Affairs, 1 August 2026. Foreign Minister Sihasak argued that Andrews had not consulted his government, labelling the statement one-sided for failing to mention Thai losses.141Thailand formally submitted its objections to the Office of the UN High Commissioner for Human Rights and the UN Human Rights Council. “Thailand rejects UN expert’s Cambodia report, cites lack of balance”, Khaosod English, 3 August 2026; “UNCLOS conciliation chair to be named this week”, Bangkok Post, 12 August 2026. Andrews stated that he had sent a draft of his statement to Thailand two days before it was issued but had received no response. “UN envoy says Thailand received draft but did not respond”, Khaosod English, 8 August 2026.

C. Nationalism as Policy Constraint

Thailand’s policy appears to be conditioned by consideration for the views of ultranationalist Thais, including serving and former military officers, who espouse the narrative of lost territories and oppose even the appearance of conciliation.142Crisis Group interviews, analyst; senior official, Bangkok, July 2026. “The land border has grown into an emotional issue”, a senior security official said. “The government can’t back down”.143Crisis Group interview, senior security official, Bangkok, April 2026. In November 2025, Anutin was compelled to apologise to the public for suggesting that Thailand had encroached on Cambodian territory, pledging that “that there is no possibility that Thailand will lose any territory, sovereignty, honour or dignity”.144“PM sorry for border gaffe”, Bangkok Post, 3 November 2025. Privately, Thai officials acknowledge that Bangkok finds the status quo acceptable.145Crisis Group interviews, senior official, Bangkok, April 2026; retired senior Thai military officer, Bangkok, June 2026. As one put it: “For domestic political reasons, this works well. There’s no strong desire to normalise [relations]”.146Crisis Group interview, senior official, Bangkok, April 2026. According to a Thai analyst, when the government cites “public sentiment” as a justification for a hard line on Cambodia, it may be understood as a euphemism for “military sentiment”.147Crisis Group interview, analyst, Bangkok, July 2026.

In the campaign for February’s general election, Anutin rode a wave of Thai nationalism generated by conflict with Cambodia. Aware that Thai nationalists have been criticising the two border memoranda since 2008, he proposed a referendum on cancelling both MOU 43 (land border) and MOU 44 (maritime border). He eventually dropped the referendum idea after the Council of State found that it might be unconstitutional, but he nonetheless pledged to withdraw from MOU 44, while keeping the option open on MOU 43.148“Anutin government plans referendum on Thai-Cambodian MoUs”, Thai PBS World, 25 September 2025; “Council of State clarifies referendum on MOU termination after House dissolution violates constitution”, The Nation, 17 December 2025; “Anutin pledges to scrap maritime MOU in final election rally push”, The Nation, 7 February 2026.

1. MOU 43

Thai critics of MOU 43 argue that it failed to end Cambodian encroachment and that it disadvantages Thailand by relying on the French 1:200,000 scale map.149“Not the right path to peace”, Bangkok Post, 28 June 2025; “Govt ‘has legal grounds’ to end MoU with Cambodia”, Bangkok Post, 9 October 2025. Before Anutin dissolved parliament in December 2025, the army asked the government to assess whether MOU 43 remained apposite.150Crisis Group interview, senior official, April 2026. See also “New government faces MOU 43 dilemma as Cambodia pushes JBC talks”, The Nation, 2 January 2026. Anutin suggested that progress had been made under its provisions in demarcating portions of the border.151“PM calls for border MoU updates”, Bangkok Post, 11 January 2026.

In May, Anutin declared that “for Thailand, the 1:200,000 scale no longer exists”, raising questions about Thailand’s adherence to the 1907 treaty.152“Thai PM firm on sovereignty, declaring colonial-era maps ‘no longer exist’ for Bangkok”, The Nation, 27 March 2026. Thai political scientist Surachart Bumrungsuk notes that the colonial-era maps are the only legal tools available for resolving conflicts over the border. Rejecting them is tantamount to rejecting the treaties themselves, which is “practically impossible and historically flawed”.153“Surachart Bumrungsuk, ‘Respectfully submitted to the prime minister: Subject: Map demarcating the land border between Thailand and Cambodia’”, Matichon Weekly, 31 May 2026. While some Thai nationalists object to the Annex I map, there is no clamour for revoking the Franco-Siamese treaties. Nor is there a practical mechanism for doing so. Moreover, the 1:50,000 scale Thai military map has no legal standing under international law. Surachart warned that Thailand risked falling into a “legal trap” should the issue be adjudicated again by the ICJ.154Surachart also notes that the Thai military map is printed with the words “boundary representation is not necessarily authoritative”. Ibid.

Meanwhile, a Senate ad hoc committee examining MOU 43 recommended on 24 March that Thailand withdraw, citing six reasons, including its reference to the Annex I map of the 1907 Treaty. Importantly, it also mentioned the changed circumstances following the fighting in December 2025: the committee’s chairman, Noppadol Inna, said the fact that Thai troops had “recovered” fifteen disputed areas weighed heavily in the committee’s decision.155“Senate panel urges end to MOU 43 over repeated Cambodian breaches”, The Nation, 24 March 2026. In his reasoning, the 27 December joint statement provision that troops must remain where they are supersedes MOU 43, which says neither side may “carry out any work resulting in changes of environment of the frontier zone”.156Ibid.; MOU 2000, Article V.

2. MOU 44

In December 2025, the same senate committee had also recommended withdrawing from MOU 44. Anutin, who had promised to annul it during his campaign, included the decision in his government’s policy statement following the February election, which the National Security Council endorsed on 23 April.157“Anutin pledges to scrap maritime MOU in final election rally push”, op. cit.; Mongkol Bangprapa, “Security Council scraps MoU 44, citing stalled talks, rising tensions with Cambodia”, Bangkok Post, 23 April 2026. Two weeks later, the government formally withdrew from MOU 44.158“For Thailand, MoU 44 no longer exists, Thai PM says”, Thai PBS World, 5 May 2026. Anutin has since been at pains to explain that the decision was unrelated to the Cambodia conflict, but instead based on the memorandum’s failure to produce results after only five meetings over 25 years.159“Fence project under way – Thailand moves to secure vulnerable crossings”, The Nation, 24 April 2026.

Cambodian officials had warned that Thai withdrawal from MOU 44 would leave them with “no choice” but to pursue compulsory conciliation under UNCLOS.160“Cambodia to pursue compulsory conciliation under UNCLOS if Thailand revokes MoU”, Phnom Penh Post, 4 May 2026. In announcing the decision to invoke compulsory conciliation on 2 June, Hun Manet said it would “[bring] dialogue into a structured international framework recognised by both countries”.161“UNCLOS underway; Cambodia lodges formal request for maritime reconciliation”, Phnom Penh Post, 2 June 2026. Established under UNCLOS Annex V, compulsory conciliation is a dispute settlement mechanism in which parties select two experts each to sit on a commission, who then select a fifth to chair the body; the resulting recommendations are non-binding but serve as a basis for negotiations. Bangkok has acquiesced to compulsory conciliation, but made its dissatisfaction clear, with Foreign Minister Sihasak noting it would “unavoidab[ly] … affect talks on restoring relations, border security and … boundary issues”.162“Thailand to join UN maritime arbitration with Cambodia, halts other two-way talks”, Reuters, 5 June 2026; “Sihasak warns Hun Manet’s maritime move could shut door on wider Thai-Cambodian talks”, The Nation, 3 June 2026. Thailand appointed Rüdiger Wolfrum (Germany) and Albert J. Hoffmann (South Africa) as its two conciliators, while Cambodia appointed Peter Taksøe-Jensen (Denmark) and Jean-Marc Thouvenin (France). In mid-August, these experts selected Australian diplomat Katrina Cooper as the commission’s chairperson. Anutin later affirmed that Thailand would suspend participation in the JBC and GBC. He added that Bangkok would not discuss renewing relations until conciliation concludes.163“Thailand to join UN maritime arbitration with Cambodia, halts other two-way talks”, Reuters, 5 June 2026; “PM appoints Sihasak to lead UNCLOS process, vows to freeze JBC and GBC talks with Cambodia”, Thai PBS World, 5 June 2026. A Thai analyst observed that, as there was no legal rationale for linking compulsory conciliation with discussions of the land border, this stance reflected Bangkok’s anger with Cambodia.164Crisis Group interview, Thai journalist, Bangkok, June 2026.

The compulsory conciliation process commenced on 15 September in Singapore, with opening statements by the two foreign ministers. Cambodian Foreign Minister Prak Sokhonn called the process “a means to rebuild trust”, expressing hope that the commission could help the parties “turn a new page for their mutual benefit”.165“Opening statement of the agent of the Kingdom of Cambodia, first meeting of the Conciliation Commission”, 15 September 2026.His counterpart Sihasak’s remarks struck an uncompromising note, citing the “broader context” of Cambodian provocations as the cause of the breakdown in relations.166“Thailand’s statement at the first meeting of UNCLOS Conciliation Commission”, 15 September 2026.

VI. Averting a Third Round

Demarcating the land border is essential if the two countries are to remove disputed territory as a source of conflict, leading to the loss of hundreds of lives over the past eighteen years. The means of specifying the land border already exist: the JBC has already demarcated three quarters of it. The main impediment is not technical complexity – the revised 2003 Terms of Reference and advantages offered by light detection and ranging should suffice – but rather the mistrust between Bangkok and Phnom Penh. Given events of the past year, there are genuine worries on both sides that a third round of fighting is likely – a former high-ranking Thai officer even called the prospect “inevitable”.167Crisis Group interviews, diplomat, Phnom Penh, February 2026; journalist, Bangkok, April 2026. See also “Ex-deputy commander of Second Army Area warns third round of fighting ‘will happen’”, The Nation, 28 January 2026.

Ideally, third-party mediation would make the necessary compromises more politically palatable. As Hun Sen noted in June 2025, any Cambodian or Thai leader who retreats from maximalist positions at this point would risk incurring public disapproval.168“Selected Comments of Samdech Akka Moha Sena Padei Techo Hun Sen, President of the Senate, on the Cambodia-Thailand Border Issue”, 2 June 2025. A disinterested third party could shield decision-makers from some of the political costs of compromise. The most logical candidate to play such a role remains the ICJ. Even if many in Thailand regard the ICJ’s 1962 ruling on Preah Vihear as unjust, it does not establish a binding precedent for other disputed areas of the land border. If Cambodia and Thailand agreed to have the court rule on all these areas, it could very well lead to an equitable resolution.169William Roth, “Tackling Thai-Cambodian border row”, Bangkok Post (editorial), 12 November 2025.

Unfortunately, such a path is, for now, politically untenable in Thailand, both because of bitterness over the 1962 ruling and the establishment’s objections to internationalising the conflict. The reality of heightened nationalism is that the Thai government is unlikely to attempt to sell the public on trading even a small amount of territory for peace.170Jones and Narut, “The Sovereignty Straitjacket”, op. cit. Prime Minister Anutin was rewarded at the polls for maintaining a hard line on Cambodia. In turn, he is intent on keeping the Thai military’s support. He also does not wish to run afoul of right-wing nationalists who perceive bargaining as a betrayal of sacrifices, military and civilian, in the 2025 fighting.171“New government faces MOU 43 dilemma as Cambodia pushes JBC talks”, The Nation, 2 January 2026. Furthermore, conflict with Cambodia has allowed the Thai military to burnish its image, which had been sullied by its overt political role, including coups d’état.172Crisis Group interviews, journalist, Bangkok, April 2026. In this charged environment, those advocating compromise risk being labelled traitors.173Crisis Group interviews, Western diplomat, Phnom Penh, February 2026; senior official, Bangkok, July 2026.

The costs of conflict are not high enough to impel [Thai and Cambodian] leaders toward a resolution.

More broadly, political elites in both countries perceive benefits from the conflict, principally from popular support arising from nationalism and as a distraction from domestic economic and political problems. For decision-makers, especially in Thailand, these benefits continue to outweigh the conflict’s costs, whether economic or reputational. In any event, the costs of conflict are not high enough to impel leaders toward a resolution. Cambodia adapted to the border closure better than many anticipated, though it has compounded pre-existing economic pressures as time goes by, contributing to a marked slowdown in growth.174Crisis Group interview, government minister, Phnom Penh, February 2026. See also “IMF Executive Board Concludes 2026 Article IV Consultation with Cambodia”, International Monetary Fund, 28 September 2026. The IMF projects growth to slow to 3 per cent in 2026, from 5.3 per cent in 2025. In any case, disruptions of bilateral trade have been damaging, but not bad enough to trigger a policy change.175Closure of the land border caused trade to decline by 40 per cent to $1.3 billion for the first half of 2026, year-on-year, according to Cambodian government data. “Cambodian economy suffers as Thai conflict blights bilateral trade”, Nikkei Asia, 24 July 2026. Some 900,000 Cambodian migrant workers returned from Thailand in 2025; two thirds of them found employment, though generally lower-paid. The UN estimated remittance losses at $277 million in 2025 and $665 million in 2026. “Socio-economic Impact Assessment of Cambodia–Thailand Border”, UN, April 2026, p. 10.

Perhaps the most significant obstacle is that, for now, political elites in Bangkok appear to see greater reward in hardline policies than in the risks of reconciliation. Cambodia’s leadership likewise sees benefit in confrontation, in the form of popular nationalist fervour, though another round of fighting could shift Phnom Penh’s calculus, as further military setbacks could fracture the Hun family’s coalition.176Crisis Group interviews, Phnom Penh, February and May 2026. Hun Sen told local officials that the CPP’s policy on the border dispute would be a campaign issue in the 2027 commune elections. “Ruling CPP to use border dispute issue as 2027 commune election campaign material”, CamboJA News, 1o June 2026. In these circumstances, reconciliation in the near term is unrealistic. Some argue that the conflict cannot be resolved until politics in both countries become more pluralistic and democratic, thereby weakening the hold of established elites.177Crisis Group interviews, academic, Phnom Penh, February 2026; journalist, Bangkok, April 2026.

Yet, given the dismal state of bilateral ties, modest steps toward improved relations are as imperative as they are difficult. Until the land boundary is agreed upon, the issue will remain a potential trigger for war. Even in the absence of further combat, the border closure and suspension of trade is immiserating people living along the frontier, depriving both countries of revenue and eroding ASEAN cohesion in a period of major-power competition and flux in the international order.

Delaying border demarcation [between Thailand and Cambodia] only heightens the risk of renewed fighting.

To begin with, Bangkok and Phnom Penh should restore normal diplomatic relations by exchanging ambassadors, signalling a desire to improve the relationship, enhance communication and start rebuilding trust. Secondly, the JBC should resume its work as soon as possible, and the GBC should convene as necessary.178In July, Prime Minister Anutin appointed retired General Somsak Rungsita, a former director of the National Security Council, to lead Thailand’s JBC delegation. Crisis Group interview, senior official, Bangkok, July 2026. The December 2025 ceasefire commits both parties to “refer to the Joint Boundary Commission to resume, at the earliest, the survey and demarcation works … to achieve lasting peace along the border”.179“Joint Statement of the 3rd Special GBC”, op. cit. Given the prohibition on the use of force in determining international boundaries, there is no legitimate alternative to jointly negotiating the boundary line and withdrawing Thai troops from areas that are indisputably Cambodian territory. Delaying border demarcation only heightens the risk of renewed fighting.

Thirdly, the neighbours have a politically acceptable platform for cooperation on demining and disposing of explosive remnants of war, which is a priority for both countries.180Thailand acknowledged using cluster munitions in 2025, defending their use as directed at military targets. The Cambodian Mine Action Centre estimates that Thai M42, M46 and M85 submunitions affected nearly 300,000 hectares in 349 villages. Neither Cambodia nor Thailand is party to the 2008 Convention on Cluster Munitions. “Cluster Munition Monitor 2026”, Cluster Munition Coalition, September 2026, pp. 24-25; “Third Review Conference condemns cluster munitions use, CMAC chief highlights impact of Thai shelling”, Agence Kampuchea Presse, 29 September 2026. The December 2025 ceasefire agreement stipulates that the two countries “work together to make timely progress on demining efforts along the border”.181“Joint Statement of the 3rd Special GBC”, op. cit. To date, however, no such cooperation has taken place.182Crisis Group interview, senior official, Bangkok, July 2026. To some extent, Thailand has lessened the urgency by unilaterally clearing mines in the disputed areas it holds, but nevertheless the two sides should undertake whatever joint efforts they can. Cambodia should destroy any remaining antipersonnel mine stocks, reaffirm to its forces that mine use is prohibited and report these steps in its annual transparency reports under Article 7 of the Mine Ban Treaty.183“Investigation into New Use of Antipersonnel Landmines on the Thai-Cambodia Border”, op. cit. These actions could help build trust with Thailand.

Both governments would serve their own interests by toning down statements that have hardened opinion and narrowed the room for compromise. Cambodia, in particular, would benefit from speaking with one voice on the border. Hun Sen’s statements, especially in 2025, attacked Thai leaders personally and raised tensions. Hun Sen often speaks before the prime minister, setting a line from which Hun Manet cannot easily depart.184Crisis Group interviews, Phnom Penh, February and May 2026. Leaving border matters to the prime minister, the foreign ministry and the bilateral mechanisms would give Cambodia a more coherent posture and Hun Manet room to seek a new relationship with Bangkok. Restraint is also needed on the Thai side, where senior military officers accused Hun Sen of lying and labelled him the real commander of Cambodian forces during the December fighting.185“RTA says Hun Sen lied, ordered provocative acts against Thailand”, The Nation, 10 December 2025. Such charges may play well at home, but they make it harder for Thai officials to treat Hun Manet as the preferred counterpart.186Crisis Group interview, senior official, Bangkok, September 2026.

International bodies and foreign states lack sufficient leverage to push [the Thai and Cambodian officials] to the negotiating table.

International bodies and foreign states lack sufficient leverage to push the sides to the negotiating table or otherwise decisively influence the course of events. U.S. diplomats remain engaged, but Washington is preoccupied with the Middle East war and shows little appetite for leading mediation efforts.187“US to provide $45m for Thailand-Cambodia ceasefire”, Nikkei Asia, 9 January 2026. For its part, China is unlikely to risk souring its relationship with either country by attempting to impose an agreement touching on the sensitive issue of sovereignty. Beijing should nevertheless intensify its Track II efforts, which have provided a welcome platform for civil society engagement and could furnish creative ideas for mending people-to-people ties.188“Summary Report: The Second China-Cambodia-Thailand Track II Dialogue, 20-21 April 2026, Beijing, China”. On file with Crisis Group.

For its part, ASEAN should play a greater role. Ceasefire monitoring could help build confidence between the two sides, but the current configuration of the ASEAN Observation Teams leaves that potential unrealised. The teams, staffed by military attachés and ASEAN representatives based in Bangkok and Phnom Penh, can observe border areas only with the host country’s permission and coordination.189“Domestic pressure holds Thailand-Cambodia peace deal hostage”, Thai PBS World, 30 October 2025. Consequently, the teams have become implicated in the rival information strategies, with both Bangkok and Phnom Penh using site visits to cast blame on their adversary.190Crisis Group interview, analyst, Bangkok, April 2026. See also “Can ASEAN keep the Thailand-Cambodia peace?”, South China Morning Post, 5 July 2026. Both sides should permit observers greater independence.191Crisis Group interviews, diplomat, Phnom Penh, February 2026; senior official, Bangkok, July 2026.

VII. Conclusion

The fighting in 2025 has given way to an uneasy ceasefire that leaves Cambodia and Thailand no closer to resolving the underlying border dispute. With nationalism running high on both sides, political elites in Bangkok and Phnom Penh perceive greater rewards in hardline posturing than in compromise. To prevent the recurrence of a conflict that has already caused hundreds of deaths and displaced over a million people, Cambodia and Thailand will eventually have to survey and demarcate the land border, requiring compromise on both sides.

Current prospects for a rapprochement are poor, however, and foreign states lack the leverage or commitment to impose a settlement. In the near term, the priority should be modest steps: restoring normal diplomatic relations by returning ambassadors, resuming the JBC’s technical demarcation work without preconditions and expanding cooperation on demining. The two sides should also permit ASEAN Observer Teams a more independent monitoring role. None of these measures will resolve the territorial dispute, but they could help rebuild the trust and communication needed to manage tensions and reduce the risk of renewed violence while a comprehensive settlement remains politically out of reach.

Bangkok/Phnom Penh/Brussels, 9 October 2026