Cambodia-Thailand border: Phnom Penh’s patience against the fait accompli

Twenty months after the first ceasefire, Thai forces are demolishing houses, digging bunkers and drilling wells on land Cambodia claims. Phnom Penh answers with protest notes and legal proceedings. On 15 September, a United Nations conciliation commission opens its work in Singapore.

The ASEAN Observer Team at the Cham Yeam border checkpoint, tasked with monitoring the ceasefire between Cambodia and Thailand. @AKP

On 31 August, Thai soldiers destroyed two Cambodian houses in the Boeung Trakoun area of Trapeang Samraong village, Kork Romeat commune, Thmar Puok district, Banteay Meanchey province. Heavy machinery then levelled the ground and raised an earthen embankment. Between 1 and 3 September, further fortifications went up near O Khla Khmum pagoda in O’Smach, Oddar Meanchey province. Between 4 and 7 September, a well was drilled at Chouk Chey. On the 7th, more civilian structures were razed at Prey Chan.

These events are listed in a statement from Cambodia’s Ministry of Foreign Affairs dated 8 September. Bangkok had not responded publicly by the time of publication. They add to a ledger Phnom Penh has kept since January 2026: razor wire, shipping containers, trenches, and a Royal Thai Air Force helicopter that entered 400 metres into Cambodian airspace on 3 September near the Daung border checkpoint in Battambang.

Cambodia protests. It does not shoot.

Two wars and two ceasefires in eighteen months

The July 2025 fighting lasted five days and killed at least 48 people according to tallies consolidated since, displacing more than 300,000 on both sides. The 28 July ceasefire, obtained in Kuala Lumpur under Malaysian mediation and American tariff pressure, was completed on 8 August by a thirteen-point agreement.

On 26 October 2025, Hun Manet and Anutin Charnvirakul signed a peace accord before Donald Trump and Anwar Ibrahim, providing for the withdrawal of heavy weapons, joint demining and the release of eighteen Cambodian soldiers captured in July. On 10 November, a mine wounded Thai soldiers on patrol in Kantharalak district, Si Sa Ket province — two according to the Thai army, four according to Human Rights Watch. It was the seventh such blast in four months. Bangkok accused Phnom Penh of laying fresh mines and suspended the accord the following day, the prisoner release included. Cambodia denied it.

The second war began on 7 December and ran for twenty days, with F-16 sorties, rocket fire and artillery barrages. Reuters counted at least 101 dead. Cambodia’s Interior Ministry recorded 32 civilians killed and 95 wounded on the Khmer side; Bangkok reported 25 soldiers and one civilian. At the peak, between 25 and 27 December, more than 640,000 Cambodians had fled.

The 27 December ceasefire, signed at Chanthaburi by the two defence ministers, froze positions along a “troop deployment line”, tasked the Joint Boundary Commission with resuming its work “at the earliest opportunity”, and provided for the return of the displaced. The eighteen Cambodian soldiers were handed back on 31 December, after 155 days in custody.

The joint commission has still not met on the contested sectors.

What Cambodia calls occupation

In February 2026, Hun Manet told Reuters that Thai forces were holding positions “deep” inside Cambodian territory, “further beyond even Thailand’s own unilateral claim”. Government spokesman Pen Bona put the number of civilians unable to go home at close to 80,000, with roads cut by razor wire and containers. By May, the Cambodian count had reached around a thousand containers.

The same place names keep recurring: Prey Chan, Chouk Chey and Boeung Trakoun in Banteay Meanchey; O’Smach, the temples of Ta Krabey and Ta Muen Thom, Chob Angkunh and Chouk Krous in Oddar Meanchey; An Seh, Ta Thav and Phnom Trap in Preah Vihear; Thmor Da and Phluk Domrei in Pursat.

Two episodes in August and September hardened the tone. On 23 August, Anutin Charnvirakul visited his troops at An Seh, which Bangkok calls Chong An Ma and places in Nam Yuen district, Ubon Ratchathani province, and which Phnom Penh locates in Choam Ksan district, Preah Vihear. The Cambodian statement of 25 August called it a deliberate attempt to legitimise an occupation.

On 7 September, Thai Air Chief Marshal Prapas Sornchaidee led members of the ASEAN Observer Team based in Thailand, along with Thai and international journalists, on a tour of a site of more than 80 hectares at O’Smach, presented as a former online scam compound: 157 buildings, 29 of them allegedly used for cybercrime. The delegation entered through the Chong Chom crossing. Phnom Penh describes this as “an unlawful assertion of Thai administrative authority” and rejects the use of crime suppression “as a pretext” for territorial violation.

This is the core of the Cambodian argument: by building permanent structures, bringing third parties on site and altering the physical condition of the land, Bangkok is manufacturing facts on the ground designed to weigh on a demarcation that has never taken place. The Cambodian ministry treats this as a breach of the 14 June 2000 memorandum of understanding on the survey and demarcation of the land boundary, as much as of the 27 December text.

The Thai case

Bangkok disputes that reading. Thailand’s joint information centre replied as early as January 2026 that its forces were strictly respecting the agreed deployment line and that their movements amounted to patrolling, demining and securing the area. After the An Seh row, Marshal Prapas added that containers and razor wire do not constitute a boundary, and that the land dispute belongs before the joint commission, with its experts and its survey work.

Thailand advances three grievances. Antipersonnel mines, first: seven incidents between July and November 2025, more than a dozen wounded and several amputations. Both countries are parties to the Ottawa Treaty. In July 2025, the Thai army said it had found ten freshly laid Russian-made PMN-2 mines, a model it does not hold. Cambodia disputes the claim and points to war remnants: the Cambodian Mine Action Centre estimates four to six million mines remain scattered across the country. No independent assessment has settled the question.

Online scam compounds, next, which Bangkok presents as a direct threat to its nationals and grounds for security operations. Aggression, finally: in a letter to the United Nations Secretary-General dated 19 September 2025, the Thai mission accused Phnom Penh of sending civilians — women, children and monks among them — to tear down razor wire in order to provoke an incident, and reported four Thai police officers injured.

Human Rights Watch, which documented both rounds, notes that each army used explosive weapons with wide area effects in populated zones. The organisation also records that Thailand is the only one of the two whose use of cluster munitions has been established. The Cluster Munition Monitor 2026, published on 8 September, lists it among the five states not party to the 2008 convention that used such weapons between mid-2025 and mid-2026 — in this case in Cambodia, which is itself among the nine countries where new casualties were recorded in 2025.

Preah Vihear: 562 damaged areas

The report of the joint UNESCO-ICOMOS advisory mission, released on 9 September, provides an independent measure of the damage. The experts, on site from 1 to 6 March 2026, recorded 142 damaged areas from the July 2025 attacks and 420 from those of December. They describe the scale of destruction as “incomparable” with that of earlier conflicts around the temple, write that “no area was spared”, and assess Preah Vihear as being under “serious and specific danger”.

The temple has been a World Heritage site since 2008. The International Court of Justice awarded it to Cambodia in 1962.

The World Heritage Committee, meeting in Busan in July 2026, unanimously adopted a decision condemning the destruction of World Heritage properties during armed conflict, under the 1954 Hague Convention among other instruments. The text names no state. The Thai delegation requested a right of reply after the Cambodian intervention.

Patience as strategy

Asymmetry explains much of it. Thailand has more than 70 million inhabitants, Cambodia around 17. Its army is larger, better equipped, and has a combat air force Phnom Penh does not. Asked in February by Fox News about possible retaliation, Hun Manet replied that he did not believe a war could be stopped with a war. In May, addressing veterans, he refined the formula: if one per cent of the door remains open to negotiation, Cambodia will take it; that does not mean kneeling or handing over land.

This patience has a legal logic, which the Interior Ministry summarised on 19 August: so long as the territorial sovereign protests continuously, an unlawful occupier acquires no permanent right of possession. Every diplomatic note is a piece of the file.

It also carries a measurable cost. The land border has been shut since late June 2025, and Anutin Charnvirakul repeated in Paris in May that reopening was out of the question. Bilateral trade fell to $1.61 billion over the first seven months of 2026, against $2.4 billion a year earlier. International tourist arrivals in Cambodia dropped 47.9 per cent in the first half, to 1.75 million. Close to 890,000 Cambodian migrant workers had returned from Thailand by the end of September 2025, and remittances fell 37 per cent over the year. Phnom Penh launched a $1.24 billion crisis-response programme in early September. On the Thai side, the bilateral business council estimated in May that land trade losses had reached 180 billion baht and that 30 per cent of border businesses had closed.

The human cost reads more slowly. On 19 August, the Interior Ministry still counted 18,703 people unable to return home, among them 9,437 women and 6,066 children. Fifteen schools and seven health centres remained closed in Oddar Meanchey, Banteay Meanchey and Preah Vihear. The same assessment listed 1,558 houses, 26 schools, 14 hospitals, 19 pagodas and four ancient temples damaged.

The wager on law

Lacking ground, Phnom Penh has chosen the courts. On 16 June 2025, Cambodia brought four sectors before the International Court of Justice: Ta Muen Thom, Ta Muen Toch, Ta Krabey and Mom Bei, in the Emerald Triangle. Thailand has not recognised the Court’s compulsory jurisdiction since 1960 — a position shared by 118 other UN member states — and declines to take part. The case is stalled.

The maritime track has fared better. On 5 May 2026, the Thai cabinet unilaterally revoked the 2001 memorandum of understanding that had framed twenty years of negotiation over the two countries’ overlapping maritime claims. On 2 June, Cambodia triggered the compulsory conciliation provided for under Annex V of the United Nations Convention on the Law of the Sea, a procedure that does not require the other party’s consent. The commission constituted under the auspices of the Permanent Court of Arbitration holds its first meeting in Singapore from 14 to 16 September. Opening statements on the 15th will be webcast live in Khmer, English and Thai. Prak Sokhonn, Deputy Prime Minister and Minister of Foreign Affairs, will speak for Cambodia, assisted by Lam Chea, Minister in charge of the State Secretariat of Border Affairs.

The precedent invoked in Phnom Penh is that of Timor-Leste and Australia, whose conciliation produced a maritime boundary treaty in 2018. What is at stake here are the hydrocarbons of the Gulf of Thailand.

Bangkok responded by tying the two files together: since Cambodia went to UNCLOS, there would be no further point in discussing the land boundary. Hun Manet called the argument “a little bit inaccurate and a little bit unfair”, noting that it was Thailand that removed the only existing bilateral framework. Hun Sen, for his part, listed in June the successive reasons for delay advanced by Bangkok — dissolution of parliament, a caretaker government without a mandate, an unappointed commission chair, then the recourse to UNCLOS — before asking Cambodians to be patient a while longer.

What could tip the balance

Anutin Charnvirakul dissolved parliament in December 2025, at the height of the fighting. His Bhumjaithai party won 192 of 500 seats on 8 February 2026, the first victory for the royalist-conservative camp this century, and he was reconfirmed in March by 293 votes. Firmness at the border is a domestic political asset, not merely a military posture. The wall promised during the campaign is going up: a first 1.3-kilometre stretch completed in late July at Pong Nam Ron, Chanthaburi province, 23.6 kilometres planned in Sa Kaeo, roughly 7 million baht per kilometre, funded in part by a royal foundation.

Cambodia has made the opposite wager: accumulate legal titles and international findings, and wait. The UNESCO report, the cluster munitions Monitor and the Busan decision are the first dividends of that line. They do not give anyone back a house in Prey Chan.

On 15 September in Singapore, for the first time since the crisis began, the two countries will plead before a body neither can walk away from with a press release.