Synopsis: Cambodia has rejected Thailand’s allegations concerning the ongoing border dispute in a letter circulated by the United Nations, calling for an end to what it describes as unlawful military occupation, the resumption of joint boundary demarcation and the safe return of more than 20,000 displaced Cambodian civilians.
Cambodia has formally challenged Thailand’s account of the ongoing border dispute in a letter to United Nations Secretary-General António Guterres, accusing Bangkok of distorting historical facts, continuing military incursions into Cambodian territory and failing to fully implement the December 2025 ceasefire agreement.
The letter, dated September 29 and published by the United Nations on October 1 as General Assembly document A/81/402, was submitted by Cambodia’s Permanent Representative to the UN, Ambassador Keo Chhea, in response to remarks delivered by his Thai counterpart, Cherdchai Chaivaivid, during the General Debate of the 81st session of the UN General Assembly on September 28.
In the letter, Ambassador Chhea expressed Cambodia’s regret that Thailand had used the international forum to repeat what Phnom Penh considers a misleading political narrative concerning the border conflict.
“Cambodia deeply regrets that Thailand chose to use the general debate to repeat a political narrative that distorts the historical record and omits key facts,” he wrote.
According to the Cambodian diplomat, Thai armed forces launched military operations against Cambodian positions along the border on July 24, 2025, before expanding their operations into a full-scale offensive on December 7, involving tanks, heavy artillery, F-16 and Saab JAS Gripen fighter jets, drones and cluster munitions.
He said Cambodia had consistently documented the attacks and lodged protests through appropriate diplomatic channels.
Despite the ceasefire established under the joint statement of December 27, 2025, Cambodia maintains that Thai forces have continued their incursions, including constructing fortifications, laying barbed wire, installing shipping containers and unilaterally altering frontier zones inside Cambodian sovereign territory.
The ambassador argued that such activities were inconsistent with the commitments undertaken by both countries to de-escalate tensions, rebuild confidence and refrain from actions that could aggravate the situation.
“Confidence is strengthened not by declarations of intent alone but by consistent implementation of agreed commitments,” he stressed.
Addressing Thailand’s allegations concerning supposedly newly planted Cambodian landmines, Ambassador Chhea categorically rejected the accusations and reaffirmed Cambodia’s commitment to the Anti-Personnel Mine Ban Treaty.
He emphasised that Cambodia’s position was rooted not only in its international obligations but also in its painful national experience of the humanitarian consequences of landmines.
The letter maintained that allegations of treaty violations must be supported by objective evidence, transparency and independent verification, reiterating Cambodia’s longstanding call for a joint, independent and impartial investigation.
Ambassador Chhea also criticised Thailand for invoking historical events to justify what Cambodia describes as present-day military incursions and the continued unlawful occupation of its territory, while failing to accept repeated invitations to promptly resume survey and demarcation activities under the Cambodia-Thailand Joint Boundary Commission (JBC).
He said the commission’s work was essential to addressing outstanding territorial claims and establishing a mutually recognised boundary in accordance with international law and existing bilateral treaties and agreements.
The letter further highlighted the humanitarian consequences of the dispute, stating that more than 20,000 Cambodian civilians remain unable to return to their homes because of continued military occupation and physical obstructions, including barbed wire and shipping containers.
Cambodia also submitted annexed maps which, according to the letter, illustrate that areas under Thai occupation extend considerably beyond those depicted in Thailand’s unilateral maps.
Referring to remarks made by a UN Special Rapporteur during a visit to the border in July, Ambassador Chhea reiterated the urgency of allowing displaced civilians to return home, quoting the UN expert as saying: “they need, and deserve, to go home”.
The ambassador welcomed Thailand’s stated commitment to the December ceasefire but insisted that Bangkok demonstrate its sincerity through concrete actions, including the resumption of JBC activities and the cessation of unilateral measures that could consolidate territorial control.
The letter also rejected Thailand’s suggestion that Cambodia was attempting to internationalise the bilateral dispute by seeking recourse through international legal mechanisms.
Cambodia argued that resorting to mechanisms established under the UN Charter and international treaties constituted a legitimate exercise of peaceful dispute settlement rather than an improper internationalisation of the conflict.
On the maritime dispute, Ambassador Chhea noted that Thailand had unilaterally terminated the 2001 Memorandum of Understanding in May 2026, despite Cambodia’s repeated appeals against the move.
He described the agreement as the only existing bilateral legal framework specifically established to address the two countries’ maritime disputes.
Following its termination, Cambodia initiated compulsory conciliation proceedings under the United Nations Convention on the Law of the Sea (UNCLOS), which the ambassador described as an opportunity to bridge differences, restore trust and establish a stronger foundation for peaceful bilateral relations.
Responding to Thailand’s expressed aspiration to open a new chapter in relations, Cambodia said it shared that objective but warned that reconciliation could not be achieved through unilateral actions or an approach based on military superiority.
“The new chapter, however, cannot be written through competing narratives or unilateral actions, nor can it commence on the dangerous premise that might makes right,” Ambassador Chhea wrote.
The letter also cited remarks attributed to Thai Prime Minister Anutin Charnvirakul in May 2026, in which he reportedly insisted that Thailand would make no concessions unless Cambodia first accepted Thai conditions.
Ambassador Chhea maintained that restoring bilateral trust required Thailand to cease activities Cambodia considers unlawful, avoid further unilateral measures and work towards de-escalation and peaceful coexistence.
Concluding the letter, he reaffirmed Cambodia’s commitment to resolving all outstanding disputes through peaceful means, in accordance with the UN Charter, international law and existing bilateral agreements.
“Geography binds our two countries together. As permanent neighbours, Cambodia and Thailand will always live side by side, and the peace, stability and prosperity of our peoples are closely interconnected,” he wrote.
