Why the Preah Vihear Dispute Between Cambodia and Thailand Persists: An Analysis Under International Law

On December 27, 2025, Cambodia and Thailand agreed to a ceasefire following four months of violence along the border, which began with a major military confrontation between the two countries on July 24, 2025. However, the situation remains fragile, as underlying tensions persist despite the absence of direct armed confrontation. Those tensions escalated on January 6, 2026, when Thai forces accused Cambodians of violating the ceasefire after one of their soldiers was wounded in a mortar attack, which was later claimed to have been caused by “an operational error by Cambodian personnel.” Despite the explanations provided by Cambodia, the Thai army warned its counterparts that in the event of another error,“Thailand may be compelled to carry out defensive countermeasures.” 

Origins of the Dispute

The border dispute concerns sovereignty over the Preah Vihear Temple and its surrounding area. To conduct a proper analysis, it is necessary to go back to its origins: sovereignty over the temple has been a subject of controversy since the early 20th century, when France and Thailand—known as Siam at that time—signed the “Convention between France and Siam for the Regulation of Certain Difficulties” in 1904, which established the border between Siam and French Cambodia based on the watershed between the basins of two rivers: the Nam San and the Nam Moun. The Preah Vihear Temple was situated within Siam’s borders, and no other demarcation was established.

In March 1907, a second treaty was signed to exchange certain territories between France and Siam. The treaty led to the establishment of a Franco-Siamese Mixed Commission to demarcate the border. However, the mapping of the territory was carried out by French officials, as Siam lacked sufficiently qualified personnel, and the map drawn in 1908 was never officially accepted by Siam. On this “Annex 1 Map,” the Preah Vihear Temple was located on Cambodian territory, and the French provided no explanation for that sudden change in the border line. Cambodia maintained this situation after its independence in 1953, leading to the adoption of different border maps by both countries.

In 1962, the ICJ ruled that the Temple belonged to Cambodia, ordering the withdrawal of Thai forces and prohibiting any military or police activity by Thailand that could infringe upon Cambodia’s sovereignty over the Temple. The main argument invoked by the court was the tacit acceptance of the 1907 map by the Siamese Government and, later, the Thai Government: Siam used and published maps showing the Temple’s location within Cambodian territory, and Siam did not raise the issue either during negotiations for the 1925 and 1937 Franco-Siamese Treaties or in Washington in 1947 before the Franco-Siamese Conciliation Commission. Furthermore, Siam did not react when, in 1930, Prince Damrong, during a visit to the Temple, was officially received by the French Resident for the adjoining Cambodian province. It was only decades later, during its negotiations with Cambodia in Bangkok in 1958, that the Thai Government raised the issue of the Temple. 

Although Thailand complied with the ICJ ruling, it erected a wire fence in July 1962, which separated the Temple from the surrounding area. The reason for this was that, because the ICJ had failed to rule on the boundary lines between the two countries, Thailand believed that, even though Cambodia owned the Temple, the surrounding area was under Thailand’s sovereignty.

The border dispute became less relevant after Vietnam invaded Cambodia in 1978. In the early 1990s, following Cambodia’s stabilization, both countries agreed to manage the dispute through short-, medium-, and long-term mechanisms: in the short term, the two countries established the General Border Committee (GBC) and the Regional Border Committee (RBC), led respectively by defense ministers and military commanders, with the aim of containing conflicts but not resolving the dispute. In the long term, the foreign ministers of Thailand and Cambodia established a “Joint Boundary Commission” at a joint cabinet meeting in Siem Reap, Cambodia, in 1997, which carried out significant work in relocating boundary markers, based on the boundary demarcations of the 1904 and 1907 Treaties and the Map in Annex 1. This mechanism was instrumental in building trust and confidence between the countries. Finally, as a mid-term mechanism, Thailand and Cambodia signed a “Framework Agreement on Economic Cooperation” in July 2001. Furthermore, they established a shared development zone along the border, the “Crescent Opportunity,” a project that connected seven provinces in each country (including Preah Vihear Province), forming a circle of cooperation and mutual benefit in this region. Thanks to this initiative, Phnom Penh and Bangkok signed an agreement in March 2004 to renovate the Preah Vihear Temple as a symbol of friendship.

Resurgence of the conflict

In July 2008, the World Heritage Committee decided to inscribe the Temple of Preah Vihear on the UNESCO World Heritage List, after Cambodia had nominated it in 2001. Thailand initially supported a bilateral nomination, but Cambodia shifted to a unilateral position. Nevertheless, Thai Prime Minister Samak Sundaravej continued to support Cambodia’s initiative, which angered Thai nationalists. Eventually, new armed clashes occurred through occasional exchanges of fire in April 2009, October 2009, January 2010, April 2010, June 2010, and February 2011. The conflict escalated between April 22 and May 3, 2011. On July 18, 2011, following a previous request by Cambodia, the ICJ issued a preliminary ruling demanding that both countries withdraw their troops from the vicinity and the wider region of the Temple, thereby creating a demilitarized zone. This never occurred; instead, both countries announced a redeployment of their troops in July 2011. 

The escalation was followed by years of calm until a Cambodian soldier was killed in a skirmish in May 2025. This led to rising tensions, which culminated in a major escalation of the conflict on July 24, when cross-border fire broke out between Thai and Cambodian soldiers in the disputed territory. The day before, a landmine explosion injured five Thai soldiers, and Thailand recalled its ambassador to Cambodia. At least 48 people were killed and thousands displaced during five days of fighting in July. Today, with the ceasefire signed on December 27 still in effect, Thai troops surround the Temple on three sides. Neither party has violated the agreement, but according to the U.S. Mission in Thailand, the security situation remains unpredictable, as Thailand continues to attempt to alter the status quo by carrying out unilateral military activities in disputed border areas.

Judicial resolution of the dispute

The border dispute between Cambodia and Thailand has become a significant case from the perspective of international law. The International Court of Justice ruled on the case in 1962 and later interpreted its judgment in 2013. 

On June 15, 1962, the ICJ ruled that the Temple belonged to Cambodia. The Court first established that sovereignty over Preah Vihear “depends upon a boundary treaty dated February 13, 1904, and upon events subsequent to that date,” which consisted of a delimitation process carried out by the Mixed Commission, as well as a series of maps, with the Annex I map (in which the Temple appears to be located on the Cambodian side) being the one on which Cambodia based its claim to sovereignty over the Temple. Thailand argued that the map had no binding force because it was not drawn up by the Mixed Commission, and that the boundary line indicated on it was not the watershed line. 

The Court did indeed conclude that the map had no binding effect at the time it was produced. However, it did confirm its technical authority and official status. The decisive issue identified by the ICJ was whether Thailand accepted the map and its boundary line or not, and the Court answered this question very clearly: Thailand received and used the maps, and did not object either in the 1925 and 1937 Treaties of Friendship, Commerce, and Navigation, nor in 1947 in Washington (Thailand did raise objections regarding the frontier line in several regions, but not regarding the Temple). Thus, the Court asserted that Thailand had acquiesced: “Qui tacet consentire videtur si loqui debuisset ac potuisset” (He who remains silent is taken to agree, if he ought to have spoken and was able to do so). 

Thailand argued that it did not have to raise the matter because it considered itself sovereign over the Temple, as evidenced by the control it exercised in the area. However, the Court found these acts to be limited and mostly local in scope, insufficient to outweigh the long-term acceptance of the map. According to the judgment, the Court found it difficult “to regard such local acts as overriding and negating the consistent and unwavering stance of the central Siamese authorities regarding the boundary line as mapped.”

To better understand the ICJ’s decision, it is essential to analyze it in light of the ICJ’s hierarchical decision-making rule in territorial disputes: the Court first considers treaties, then “uti possidetis” (a principle of international law that seeks to preserve the borders of new states emerging from former colonies), and finally effective control. The existence of a treaty or any other agreement between states is generally decisive for the ICJ. In this case, the 1904 Treaty and the tacit acceptance of the Annex I map constituted an expression of the states’ consent to the temple’s location on the Cambodian side. This explains why the ICJ did not consider other factors such as geography, culture, or ideology: international law does not function as a body of rules independent of state sovereignty, but rather respects agreements between sovereign states. The ICJ does not have the power to impose any rules on Thailand or Cambodia if they have previously agreed to manage their territorial affairs in a specific manner.

In 2013, the ICJ interpreted its 1962 judgment at Cambodia’s request. While Thailand believed there was a dispute regarding the implementation of the judgment, Cambodia claimed there was a disagreement regarding its interpretation—specifically, regarding terms such as the “vicinity” of the Temple or Thailand’s obligation to withdraw. 

The ICJ ruled that Cambodia had sovereignty over the entire Preah Vihear promontory and that Thailand had to withdraw its troops from that territory. The Court stated that this territory did not include the area designated by the Thai Council of Ministers in 1962, nor the zone claimed by Cambodia, which, in addition to the promontory, included Phnom Trap Hill.

In this case, the scope of the 2013 interpretation was directly determined by the structural limitation set forth in Article 60 of the ICJ Statute: “In the event of a dispute as to the meaning or scope of the judgment, the Court shall construe it upon the request of any party.” An analysis of what this article implies is essential to understanding the difference between an interpretation proceeding and a new judgment by the ICJ: Cambodia requested the Court to interpret its previous judgment, which meant that the ICJ was limited to clarifying those aspects of the 1962 judgment whose meaning or scope was genuinely in dispute, without any power to modify, revise, or expand the original decision. Therefore, the ICJ did not address questions such as the binding force of the boundary established by the 1962 Judgment, ownership of areas beyond the Preah Vihear promontory, whether Thailand’s obligation to withdraw was a continuing one, or whether the map in Annex I legally constituted the international boundary for all surrounding territory.

Outstanding dispute 

The conflict between Cambodia and Thailand over the Preah Vihear Temple illustrates a common problem in judicial disputes: a lack of precision in defining the dispute. The International Court of Justice, the highest judicial authority in international law, has been unable to resolve the conflict, largely due to the lack of cooperation between the two states in presenting their claims before the Court. 

The principle of “ne ultra petita,” according to which the Court cannot rule on matters beyond the scope of the parties’ claims, is essential to ensuring the proper functioning of judicial proceedings and due respect for the sovereignty of states. In 1962, the Court was asked to rule on territorial sovereignty over the Preah Vihear Temple, and the judgment established that the Temple belonged to Cambodia. In its 2013 interpretative ruling, the Court confirmed Cambodia’s sovereignty over the entire promontory on which the Temple stands and Thailand’s obligation to withdraw from that area. Nevertheless, sovereignty over the surrounding area (approximately 4.6 km²) remains in dispute, as the Court was legally limited to ruling on the matters raised by the parties.

Overall, the remaining dispute over the territory surrounding Preah Vihear Temple is largely a matter of ambiguity. Although both countries have complied with the ICJ’s decisions—with Thailand respecting Cambodia’s sovereignty over the Temple and, following the interpretation, over the promontory—they have not been able to reach an agreement regarding the disputed surrounding area. The conflict will only be resolved when both countries agree to establish a border or ask the ICJ to resolve the remaining territorial dispute, with the former option being much faster and more flexible than the latter. Until that happens, violent confrontations along the border are likely to remain unpredictable.