The Thailand-Cambodia border conflict represents one of Southeast Asia's longest-running territorial disputes, spanning over a millennium from the height of the Khmer Empire to present-day military confrontations. At its heart lies the question of sovereignty over ancient Khmer temples, particularly Preah Vihear, and the complex legacy of colonial border demarcation that continues to fuel tensions today.
The dispute stems from colonial-era mapping discrepancies in the 1904-1907 Franco-Siamese treaties, where French surveyors deviated from agreed watershed boundaries to place ancient Khmer temples in Cambodia. Despite International Court of Justice rulings, incomplete border demarcation and competing historical claims over the Khmer Empire's legacy continue to fuel nationalist sentiments and military confrontations.
The mighty Khmer Empire reaches its peak, controlling vast territories including most of modern-day Thailand, Cambodia, Laos, and southern Vietnam. Construction of Angkor Wat and Preah Vihear temple complex during the 11th-12th centuries.
Territorial boundaries during this period
Siam sacks Angkor in 1431, forcing the Khmer capital south to Phnom Penh. Over four centuries, Siam gradually annexes Cambodian territories, including northwestern provinces around Sisophon and Battambang by 1794.
Territorial boundaries during this period
King Norodom requests French protection in 1863 to avoid complete Siamese domination. The Franco-Siamese crisis of 1893 forces Siam to cede extensive territorial claims over Lao and Cambodian tributaries to French Indochina.
Territorial boundaries during this period
The Franco-Siamese treaties of 1904 and 1907 establish final boundaries between Siam and French Indochina. The 1904 treaty specifies borders along the watershed line of Dangrek Mountains, but French surveyors create maps deviating from this line, placing Preah Vihear in Cambodia.
Territorial boundaries during this period
Thailand under Plaek Phibunsongkhram allies with Japan and invades French Indochina in 1940, pursuing pan-Thai ideology to reclaim 'lost territories.' Thailand briefly annexes parts of areas ceded in 1904 and 1907, including Preah Vihear.
Territorial boundaries during this period
After French colonial forces withdraw in 1954, Thai troops occupy Preah Vihear. Cambodia protests and files suit at the International Court of Justice in 1959. The ICJ rules 9-3 in favor of Cambodia in 1962, ordering Thailand to withdraw troops.
Territorial boundaries during this period
Prince Sihanouk takes ceremonial possession of Preah Vihear in 1963, allowing Thai visitors without visas. The area becomes inaccessible due to Khmer Rouge control and extensive mining during Cambodia's civil war period.
Territorial boundaries during this period
Both countries establish Joint Boundary Commission in 1997 to demarcate borders. After Khmer Rouge collapse in late 1990s, Preah Vihear becomes accessible to religious visitors and tourists. Both governments improve access infrastructure.
Territorial boundaries during this period
Cambodia's UNESCO World Heritage nomination for Preah Vihear reignites the dispute. Thai political crisis with Yellow Shirt protests exploits the issue. Military confrontations occur, with several soldiers killed. ICJ clarifies 2013 ruling to include temple promontory.
Territorial boundaries during this period
Following the 2013 ICJ clarification, tensions subside but border demarcation remains incomplete. Tourism revenues affected by periodic flare-ups. Both countries continue to maintain military presence in disputed areas.
Territorial boundaries during this period
Tensions dramatically escalate in 2025 with the worst fighting since the dispute began. Clashes at Ta Moan temple in May precede full armed conflict breaking out in July, marking a dangerous new phase in the centuries-old territorial dispute.
Territorial boundaries during this period
The conflict has erupted into its most serious phase since the dispute began, with open armed conflict breaking out in July 2025 following escalating tensions at the Chong Bok pass. This represents a dangerous escalation in the millennium-old territorial dispute, with both nations maintaining significant military presence in contested border areas. The situation remains volatile with ongoing casualties and no clear diplomatic resolution in sight.
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