An armed confrontation broke out between Cambodia and Thailand on 24 July 2025. This was not the first time. The two neighboring Southeast Asian countries clashed in October 2008 due to rising tension over longstanding border disputes. Armed confrontations recurred from 2019 to 2011. The International Court of Justice of the United Nations intervened in July 2011 and ordered both countries to withdraw their military forces from the disputed border.

Cambodia-Thailand Relations: Border Dispute as the Main Cause of the Conflict Between Cambodia and Thailand

Nevertheless, beginning on 28 May 2025, the tension between Cambodia and Thailand reignited with a 10-minute skirmish due to the same border claim. This resulted in the death of Cambodian soldier Second Lieutenant Suon Roun. There were attempts to ease the tension through diplomatic talks, but domestic policies and actions resulted in the further deterioration of the relationship between the two countries. July 2025 marked another turning point.

French-Era Demarcation Lines and Cartography: Franco-Siamese Treaty of 1904

Border dispute is the main cause of the conflict between Cambodia and Thailand. This dispute has its roots in the ambiguity of the demarcation line emerging from the Franco-Siamese Treaty of 1904. The treaty was a convention between the Kingdom of Siam, now known as Thailand, and French Indochina, which included Cambodia, Laos, and Vietnam. It established certain border demarcations between Siam and the territories colonized by the French Republic.

The need to establish precise boundaries was critical at that time because maps and natural landmarks like rivers and mountain ridges were unclear. France wanted well-defined borders to govern its colonies effectively and reduce conflicts with Siam. The treaty sought to reduce tensions by formally ceding certain territories from Siam to France. It also allowed Siam to maintain its independence by conceding disputed territories rather than risking war with France.

Siam essentially lacked military and diplomatic leverage during the French Indochina era. Both parties also wanted to avoid the recurrence of the 1893 Franco–Siamese War. Nevertheless, due to the agreement, French surveyors and cartographers drew border lines and created maps. These maps were essential for France to secure its borders and administer its colonies. One of these maps specifically placed the Preah Vihear Temple on the Cambodian side of the border.

Dispute Over the Preah Vihear Temple: 1962 International Court of Justice Ruling

Cambodia gained independence from France in 1953. However, following this, disputes arose with Thailand about which country had sovereignty over the Preah Vihear Temple, which is an ancient temple situated on the top of Poy Tadi cliff along their border. The temple was first constructed as early as the 9th century and was completed between the 11th and 12th centuries. It was dedicated to the Hindu god Shiva and was later converted to become a Buddhist temple.

The dispute with Thailand prompted Cambodia to lodge a complaint before the International Court of Justice. The country argued that Thailand occupied the temple area despite maps created during the French colonial era showing it under Cambodian territory. Thailand noted that the temple is on its territory based on natural geographic features. The International Court of Justice ruled in favor of Cambodia in 1962 and granted it sovereignty over the temple structure.

It is important to note that the areas surrounding the Preah Vihear Temple are also disputed. These include the 4.6-square-kilometer land surrounding the temple on the Dangrek Mountain range. Other areas are also disputed. These include the Tao Man temple along Surin Province in Thailand and Oddar Meanchey Province in Cambodia, and the Tai Krabei temple near Tao Man. These areas lacked clear demarcation and have natural features that conflicted with colonial-era maps.

Modern Cambodia-Thailand Border Disputes: UNESCO Listing and Militarization

Cambodia petitioned UNESCO to list Preah Vihear Temple as a World Heritage Site. The bid was approved in 2008. However, while the bid only covered the temple itself, Thailand perceived it as Cambodia asserting sovereignty over the entire contested area. This sparked nationalist protests in Thailand. The armed forces of both countries were also mobilized along the border.

The border dispute has also become entangled in Thai internal politics. The earlier rivalry between the royalist-nationalist Yellow Shirts and the pro-Thaksin Red Shirts. Thai nationalists accused the government of giving away territories to Cambodia. The Cambodia-Thailand border dispute has since been used by several Thai politicians to advance their own political agenda.

Relations between Cambodia and Thailand somewhat eased around 2012. However, the tension resurfaced after Cambodian senior leader Hun Sen embarrassed Thai Prime Minister Paetongtarn Shinawatra, daughter of former Prime Minister Thaksin Shinawatra, leaked a phone call between them about the disputed border. The Thai government expelled the Cambodian ambassador. This has set the stage for the latest military confrontation along the disputed border.

FURTHER READINGS AND REFERENCES

• International Court of Justice. 11 November 2013. “Request for Interpretation of the Judgment of 15 June 1962 in the Case Concerning the Temple of Preah Vihear (Cambodia v. Thailand), Judgment.” ICJ Reports. 2013: 281. Available via PDF
• Yoosuk, U. 2013. “The Preah Vihear Temple: Roots of Thailand-Cambodia Border Dispute.” International Journal of Asian Social Science. 3(4): 921-929. Available online
• Wagener, M. 2011. “Lessons from Preah Vihear: Thailand, Cambodia, and the Nature of Low-Intensity Border Conflicts.” Journal of Current Southeast Asian Affairs. 30(2013): 3. Available online