Thailand’s Colonial-Era Claims: A Legacy of Unequal Treaties

Subtitle :  How the Franco-Siam Treaties of 1904 and 1907 continue to shape border tensions and historical narratives

Introduction   Thailand was never fully colonised, but its modern borders—and the disputes that surround them—are deeply rooted in colonial-era treaties. In recent years, Thailand has been accused of manipulating these historical agreements to justify territorial claims, particularly in its ongoing tensions with Cambodia.

This post explores the Franco-Siam Treaties of 1904 and 1907, their original intent, and how Thailand’s selective interpretation continues to stir controversy and complicate regional diplomacy.

📜 The Franco-Siam Treaties: Origins and Intent

In the early 20th century, Siam (now Thailand) signed two key treaties with colonial France, which controlled Cambodia and Laos as part of French Indochina.

• 1904 Treaty defined borders along the natural watershed of the Dângrêk Mountains. Intended to clarify the territorial limits between Siam and French Cambodia.

• 1907 Treaty   Adjusted borders further, transferring provinces like Battambang, Siem Reap, and Sisophon from Siam to French Indochina. These changes were meant to settle lingering disputes and solidify colonial control.

At the time, Siam was under immense pressure from European powers. These treaties were not negotiated on equal footing—they were shaped by colonial interests and geopolitical leverage.

⚔️ Modern Controversy: Preah Vihear and Beyond

Thailand’s invocation of these treaties today is most visible in its dispute over the Preah Vihear temple, a UNESCO World Heritage site perched on the border with Cambodia.

• In 1962, the International Court of Justice (ICJ) ruled that the temple lies within Cambodian territory, based on maps produced by French colonial authorities.

• Thailand has challenged the ruling, citing alternative maps and interpretations of the watershed principle from the 1904 treaty.

• Cambodia accuses Thailand of using unilateral cartography and outdated legal frameworks to assert control over land that international law recognises as Cambodian.

This isn’t just a legal dispute—it’s a clash of historical narratives, national pride, and postcolonial identity.

🧠 Thailand’s Semi-Colonial Legacy

Unlike India or Vietnam, Thailand was never fully colonised. But it wasn’t entirely sovereign either.

• Historians describe Thailand’s position as “semi-colonial”—subject to unequal treaties, foreign pressure, and territorial concessions.

• The Franco-Siam treaties are part of this legacy: imposed compromises that still haunt the region’s geopolitics.

• Thailand’s continued use of these treaties reflects a deeper discomfort with its colonial past and a desire to reclaim perceived losses.

🧭 Ethical Questions and Regional Impact

Thailand’s stance raises important questions:

• Should colonial-era treaties still define modern borders?

• What happens when one country refuses to accept international rulings?

• How do historical grievances shape contemporary diplomacy?

For Cambodia, the issue is not just territorial—it’s existential. It’s about sovereignty, justice, and the right to define its borders without interference from a more powerful neighbour.

Closing Thought   The Franco-Siam treaties were born in an era of empire and imbalance. Their continued use today—especially in defiance of international law—reveals how colonial legacies linger, not just in maps, but in mindsets.

Thailand’s challenge is not just legal—it’s historical. And until it reckons with the full weight of its semi-colonial past, these disputes will remain unresolved.