Thailand Cambodia Conflict: Focus On Legal Aspects And More

Introduction

Thailand Cambodia ceasefire renewal through the efforts of ASEAN has fructified, but is it the end of Thailand Cambodia war? The ceasefire is definitely a step towards ending the war. It is like a political intervention to get the law and order situation in control, but unless the root cause of Thailand Cambodia conflict is addressed through resolution of Thailand Cambodia border disputes, the conflict will keep getting re-ignited, leading to an extended Thailand Cambodia war. This piece, therefore, focuses on the legal aspects of Thailand Cambodia conflict.

Thailand Cambodia Border Disputes

There are long pending Thailand Cambodia border disputes deriving from the treaties signed between France (representing Indo-China) and Siam (as Thailand was then called). The convention dated February 13, 1904, modifying the stipulation of treaty dated October 3, 1893, and the treaty dated March 23, 1907, with protocol for delimitation annexed therewith, led to the demarcation of boundaries and the preparation of maps thereof.

However, the above didn’t stop the legal battle between Thailand and Cambodia (earlier part of Indo-China along with Laos and Vietnam) in the International Court of Justice (ICJ) on the question of sovereignty status of Preah Vihear Temple and its promontory (the cliff like structure on which the temple stands).

Similar sovereignty disputes also exist with respect to the following:

Ta Moan Temple Complex.
Emarald Triangle Region (the border region where Thailand, Laos and Cambodia meet and includes Preah Vihear Temple and Phnom Trap Hill).
The Villages of Ban Nong Chan and Ban Nong Ya Kaew.
Overlapping claims in the Gulf of Thailand.

Thailand Cambodia Border Dispute Resolution Approaches

Thailand and Cambodia propose different approaches for the resolution of Thailand Cambodia border disputes. Though they both agree vide the Memorandum of Understanding dated June 14, 2000 (MoU 43) that there is a need for proper demarcation of boundaries and have also set up a Joint Boundary Commission (JBC) for the same, which is co-chaired by the two countries and comprises members from both the countries, but they disagree on the scope and ambit of the JBC.

Thailand would like to claim that all legal disputes with respect to the boundaries have already been settled vide the earlier treaties, and there is only a need to execute the treaty terms through an executive body, i.e. the JBC. So, the disputes arising now are capable of being resolved through the empowered body, i.e. the JBC, that has been setup vide MoU 43. In case the dispute is not getting settled through the JBC, it is a dispute internal to MoU 43 with respect to its application, and Article VIII of MoU 43 provides for its settlement through peaceful consultation and negotiation. The exact wordings of the said Article VIII are as follows:

Any dispute arising out of the interpretation or application of this Memorandum of Understanding shall be settled peacefully by consultation and negotiation.

On the other hand, Cambodia would like to claim that all Thailand Cambodia border disputes are basically with respect to the interpretation of the above mentioned treaties, the demarcation exercises and the maps prepared thereof. The 1962 and the 2013 ICJ rulings with respect to Preah Vihear and its promontory also basically dealt with interpretation of the above mentioned documents as explained by the external corroborative evidence. So, there is a need for legal answers with respect to the legal questions arising with respect to the interpretation of the said documents.

It is pertinent to mention here that Thailand doesn’t acknowledge the ICJ rulings with respect to Preah Vihear and its promontory as a mandate for the JBC, whereas Cambodia deems the rulings to be setting up a mandate for the JBC to demarcate the relevant frontier as per the rulings.

Kuala Lumpur Accord and ASEAN

The prime ministers of Thailand and Cambodia signed a joint statement in Kuala Lumpur, Malaysia, on October 26, 2025, in the witness of president of the United States and the prime minister of Malaysia. The two main important agreements in the joint statement were implementation of military de-escalation under the observation and verification of the AOT (ASEAN Observer Team) and the recognition of Regional Border Committee (RBC), General Border Committee (GBC), and JBC as the bilateral mechanisms to work through border related issues, including alleged encroachment in accordance with the outcome of the discussion under the JBC.

RBC and GBC are military bodies and ensure a necessary pre-conditon of safety of joint survey team constituted under MoU 43 for survey and demarcation of boundaries. Other than that, they also handle day-to-day military co-ordination with policy decisions at GBC level. Under the Kuala Lumpur Accord joint statement, these two bodies are deemed responsible for formulation of de-escalation measures and for overseeing the implementation of Thailand Cambodia ceasefire agreement under the supervision of the AOT.

So, essentially Kuala Lumpur Accord only set up a bilateral military mechanism for implementation of the Thailand Cambodia ceasefire, which failed when Thailand suspended the Kuala Lumpur Accord on November 10, 2025. The latest joint statement dated December 27, 2025, with respect to the Thailand Cambodia ceasefire facilitated by ASEAN, is signed by the defence minister of the two countries in their capacities as respective co-chairmen of the GBC, which makes it abundantly clear that ASEAN is involved only to the extent of ensuring military de-escalation.

However, it is pertinent to mention here that Kuala Lumpur Accord, by recognising the JBC as a discussion forum for resolving the alleged encroachments, actually upheld the bilateral mechanism approach of Thailand for resolving Thailand Cambodia border disputes, but, ironically, Thailand itself suspended the Kuala Lumpur Accord. Now, the reference to Kuala Lumpur Accord is limited to maintaining the spirit of the accord for the return of 18 Cambodian soldiers in the custody of Thailand and to recognition of the important role of the AOT. The reference to the JBC is only neutral for resumption of survey and demarcation work in accordance with the existing agreements.

Thus, it is clear that the fundamental dispute with respect to scope and ambit of the JBC remains unresolved. There is a definite need for the resolution of this dispute as a first step towards lasting peace and cessation of war.

The Role of ICJ and International Arbitration

There can be no gainsaying that international arbitration is subject to the soveriegnty of nations under international law. Unless sovereign nations agree to international arbitration right upto the execution of international arbitration decisions, there is hardly any enforcement mechanism availaible under international law.

Thailand is not amenable to any kind of international arbitration, whereas Cambodia wants international arbitration for resoluton of all disputes. I would however note that Thailand, unlike India, is not resistant to international mediation. Both the USA and ASEAN have mediated directly (and China, I think, indirectly) to atleast ensure a ceasefire. Of course, India-Pakistan ceasefire was also mediated by the USA, but whatever…it’s not the official position of India.

As I have noted above, ASEAN is not mediating fundamental border disputes or even preliminary disputes with respect to the scope and ambit of JBC. But, there is a definite scope for international intervention in border disputes as well, through arbitration, mediation, or judiciary (ICJ). I find the ICJ the apt body for resolution of Thailand Cambodia border disputes. However, Thailand has rescinded from the cumpulsory jurisdiction of the ICJ in 1960.

On the other hand, Cambodia has recently filed a petition before the ICJ in June 2025 for resolution of border disputes with respect to Emarald Triangle Region and Ta Moan Temple Complex. The petition has been kept in indefinite suspension because of Thailand’s rejection of the ICJ’s compulsory jurisdiction. But, it is not so that there is no justiciable issue at all before the ICJ.

Vide Article 36 of the Statute of the ICJ, the ICJ’s jurisdiction comes into operation either by the agreement of the parties, by voluntary subugation to the ICJ’s compulsory jurisdiction, or by reference to matters specifically provided in the charter of the UN or in treaties and conventions in force.

In the 1959 Preah Vihear Temple case also, a preliminary issue of law with respect to jurisdiction of the ICJ over Thailand was decided against Thailand on the finding that Thailand had not then rescinded from the compulsory jurisdiction of the ICJ as claimed by it. The ICJ noted that Thailand made the admission before the ICJ that its rejection of the ICJ’s compulsory jurisdition was only procedural, and the intention was to subject itself to the ICJ’s compulsory jurisdiction.

However, at that time, the ICJ didn’t decide the issue of the ICJ’s jurisdiction over Thailand with regards to Article 21 and 22 of the Franco-Siamese Treaty of Friendship, Commerce and Navigation dated December 7, 1937; Article 2 of the Settlement Agreement dated Novemeber 17, 1946; and the General Act for the Pacific Settlement of International Disputes dated September 26, 1928. This was because the ICJ ruled against Thailand on the first ground of Cambodia with regard to its compulsory jurisditcion itself and didn’t feel the need to adjudicate on the second ground.

The above is a justiciable issue even now when Thailand has formally and intentionally rejected the compulsory jurisdiction of the ICJ after 1960 by not extending its commitment to the ICJ’s compulsory jurisdiction. There is no occasion for the ICJ to keep the issue of its own jurisdiction pending indefinitely in a petition filed by Cambodia. Thailand also claims special bar to the jurisdiction of the ICJ under MoU 43 in reference to Article VIII above. However, this is also a justiciable issue connected to the jurisdiction of the ICJ. I am particularily expressing my opinion on this issue below as a bonus reading only.

Author’s Opinion on Thailand’s Claim of Special Bar to ICJ’s Jurisdiction

Thailand’s claim of special bar to ICJ’s jurisdiction over itself with respect to Thaiand Cambodia border disputes is similar to India’s rejection of international arbitration or mediation in Kashmir dispute. India relies on the following clause of Simla Agreement to make its claim:

That the two countries resolve to settle their differences by peaceful means through bilateral negotiations or by any other peaceful means mutually agreed upon between them. (emphasis supplied)

The use of the phrase “mutually agreed upon between them” does give a source of claim to India, though I would say it is a weak claim in absence of an explicit bar to international arbitration and mediation in the Simla Agreement, especially in view of India’s ambition to nullify/rescind the self-initiated proceedings before the UNSC in 1948.

However, MoU 43 has no expicit or implicit bar, whatsover, barring the jurisdiction of ICJ or international bodies. Article VIII only says that the issues with respect to interpretation and application of MoU will be decided bilaterally. It doesn’t make even a remote reference to Thailand Cambodia border disputes. It can’t be countenanced that the earlier treaties and maps referred in Article I of MoU 43 can be interpreted by JBC alone without any external legal help.

The mandate of the JBC is just that of an executive body. It has neither composition nor character of a judicial or quasi-judicial body. There is no direct or indirect provision in MoU 43 for appointment of legal advisors or for reference of matters to judicial forums for settlement of legal issues. The terms of reference of the JBC are also purely connected to survey and demarcation only. The JBC barring the jurisdiction of the ICJ is ludicrous to say the least, but, of course, sovereignty gives you the right to do stupid things with elan.