Thailand-Cambodia Map and the Origins of the Border Dispute

Thailand and Cambodia have shared a deep-rooted civilization since ancient times, dating back over 1,000 years to the Suvarnabhumi era. The two nations have long been geographically divided by mountain ranges and watersheds, which eventually evolved into today’s clearly defined administrative boundaries.

The most recent clashes in July 2025, resulting in both military and civilian casualties, stem from conflicting map references used by each side. This article from MyContent revisits the historical roots of this conflict and explains why Cambodia uses a 1:200,000 scale map while Thailand uses a 1:50,000 map.

Disputed Territories: Former Thai Provinces Now in Cambodia

Several Cambodian provinces were once under Siamese (Thai) sovereignty, particularly before the Franco-Siamese Treaties of 1904 and 1907, when France pressured Thailand to cede territory to French Indochina, including areas that now form part of Cambodia:

1. Battambang Province

• Controlled by Thailand as “Phra Tabong” since 1785 (Rama I era)

• Directly administered by Thailand for over 100 years

• Evidence includes Thai-stamped travel documents

2. Siem Reap Province

• Once under Siam as “Siemmarat” or “Sri Sanphet”

• Home to historic sites like Angkor Wat and Preah Vihear Temple

• Strategically important during Siam’s expansion into Khmer territory

3. Sisophon (Sri Sophon)

• Now part of Banteay Meanchey Province

• A frontier town historically used by Thailand for military campaigns into Cambodia

When Did Thailand Return These Territories?

🔹 The 1907 Franco-Siamese Treaty

• During the reign of King Rama V, Thailand ceded Battambang, Siem Reap, and Sisophon

• In exchange, France returned parts of Trat Province and nearby islands in the Gulf of Thailand

Why Did Thailand Sign the 1907 Treaty?

• Thailand (then Siam) faced immense geopolitical pressure from French imperialism

• After the Paknam Incident in 1893 (R.S. 112 Crisis), France forced Siam to surrender territory east of the Mekong (e.g., Luang Prabang, Champasak)

• France used salami tactics to gradually claim more land

• In 1904, France returned Chanthaburi but seized Trat

• Thailand traded the Khmer provinces to regain Trat and nearby islands

Strategic Diplomacy by King Rama V

• Recognized that military resistance was unwise against a colonial empire

• Opted for diplomacy to preserve national sovereignty

• Prioritized long-term independence over short-term territorial control

Conflicting Maps: The Core of the Border Dispute

The long-standing border dispute arises from different map interpretations—Cambodia uses a 1:200,000 scale map, while Thailand uses a 1:50,000 scale map. This issue dates back to the Franco-Siamese treaties and remains unresolved even in 2025.

1. Map Scale 1:200,000 (Cambodian Claim)

• Produced by French cartographers during the colonial era

• Included with the 1904/1907 treaties

• Cambodia sees this as a historic legal document

• Referenced during the 2025 Joint Border Commission (JBC) meetings

Note: In 1962, the International Court of Justice (ICJ) ruled Preah Vihear Temple belonged to Cambodia, but did not endorse the 1:200,000 map as a definitive border.

2. Map Scale 1:50,000 (Thai Claim)

• More accurate and detailed, widely used for modern topography

• Developed after WWII, enhanced between 2003–2006 using SPOT5 satellite images and WGS 84

• Thailand uses it for internal border demarcation and military patrols

• Cambodia does not recognize it as a legal reference, claiming it’s a unilateral Thai product

Summary: Roots of the Thai–Cambodian Border Conflict

• Rooted in interpretations of the 1904/1907 Franco-Siamese treaties

• Treaties referred to watershed lines and French-drawn maps (1:200,000)

• 1962: ICJ awarded Preah Vihear Temple to Cambodia but didn’t define borders precisely

• Thailand uses 1:50,000 maps for technical and statistical purposes, but they are not internationally recognized

• The 2025 border skirmishes stem from conflicting map claims and refusal to mutually recognize each other's maps

• Ongoing JBC negotiations: Cambodia insists on 1:200,000; Thailand calls for bilateral talks using 1:50,000

Strategic Dispute Over the Overlapping Claims Area (OCA)

Even without official territorial conflict over Ko Kut, the area holds high strategic and economic value. Both countries claim a ~27,000 sq. km. zone in the Gulf of Thailand, suspected to contain:

• Natural gas (11 trillion cubic feet)

• Oil and condensate deposits

Cambodia’s coast:

• Mostly shallow and muddy (e.g., Koh Kong, Kampot)

• Only one deep-sea port: Sihanoukville

Thailand’s advantage:

• Ko Kut is near vital shipping lanes and Koh Kong

• Better geological systems, making exploration easier

• Thailand has advanced infrastructure and companies like PTTEP for offshore energy

Who Has the Advantage in the OCA?

Thailand holds the upper hand in the disputed maritime zone, due to:

• Superior technology, exploration capacity, and energy infrastructure

• OCA lies within the Pattani Basin, a major gas field for Thailand

Thailand had previously removed OCA from its National Energy Plan 2024 due to negotiation deadlock. However, if joint development proceeds, Thailand could still benefit more—even under a 50:50 revenue-sharing model—thanks to better readiness.

Conclusion

The Thai–Cambodian border dispute is a complex issue rooted in colonial-era treaties, modern-day map interpretations, and economic interests, particularly in the energy-rich Gulf of Thailand. With high stakes on both sides, particularly around Ko Kut and maritime energy resources, diplomatic negotiation remains the only path to a peaceful resolution.

References

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