By: Megha Mittal, Research Analyst, GSDN

On July 24, 2025, the long-simmering border dispute between Thailand and Cambodia erupted into the most violent confrontation in more than a decade. What began with rising tensions in May sparked by incidents along their shared frontier escalated into heavy fighting across at least a dozen border sites, including areas near the historic Preah Vihear and Ta Muen Thom temples. Rooted in colonial-era boundary disputes and contested claims over ancient heritage sites, the clashes claimed at least 38 lives, mostly civilians, and displaced more than 300,000 people in both countries.

The fighting, which raged for five days, saw intense exchanges of artillery fire and accusations of indiscriminate attacks, even as both governments accused the other of violating humanitarian norms. On July 28, 2025 a fragile ceasefire was reached in Kuala Lumpur, mediated by Malaysian Prime Minister Anwar Ibrahim in his capacity as ASEAN chair, with the backing of the United States and China. The high-stakes diplomacy was further propelled by U.S. President Donald Trump’s direct intervention threatening steep tariffs and frozen trade talks unless hostilities ceased while China lent strong support to its ally, Cambodia.

International pressure, including a closed-door UN Security Council session, underscored the conflict’s regional and global significance. While both sides have since agreed to form a joint boundary committee and avoid provocative troop movements, mutual distrust and competing nationalist narratives mean the truce remains fragile. This article examines the 2025 border crisis in depth tracing its historical roots, unpacking the political and military dimensions, assessing the humanitarian toll, and evaluating the diplomatic efforts aimed at preventing a return to war.

Background

1. Historical Context of Thailand–Cambodia Relations

Thailand and Cambodia share deep historical, cultural, and political linkages, but these have been intertwined with centuries of disputes, shifting alliances, and contested borders. Their relationship has roots in the ancient Khmer Empire, which once extended over parts of present-day Thailand, influencing the Thai language, architecture, and religion. However, colonial interventions in the 19th and early 20th centuries particularly under French rule in Cambodia and British influence in Siam (now Thailand) reshaped boundaries and sowed seeds of future territorial disputes.

A key point of contention emerged around the Preah Vihear Temple, a Hindu religious site located atop a 525-meter cliff along the Dangrek Mountains. In 1962, the International Court of Justice (ICJ) ruled in favor of Cambodia, granting sovereignty over the temple. However, Thailand maintained claims over surrounding areas, leading to sporadic tensions. The post-Cold War era initially opened avenues for greater cooperation, as both countries engaged in trade, tourism, and regional integration under ASEAN. Yet, historical grievances and competing national narratives continued to simmer beneath the surface, ready to resurface whenever nationalist politics or external events stirred the waters.

2. Border Disputes and Escalations Prior to 2025

Border tensions between the two countries have periodically flared, often triggered by disputes over territory adjacent to the Preah Vihear Temple and other less-defined boundary sections. The most notable modern escalation occurred between 2008 and 2011, when UNESCO’s recognition of the Preah Vihear Temple as a World Heritage Site reignited hostilities. Skirmishes along the border left dozens dead, displaced thousands, and strained bilateral ties.

Although ceasefire agreements were reached and ASEAN mediation was attempted, mutual suspicion persisted. The Cambodian political landscape, dominated by long-serving Prime Minister Hun Sen, frequently leveraged nationalist sentiment over territorial integrity, while Thailand’s domestic politics marked by military influence, political protests, and competing power factions sometimes used the dispute to rally domestic support.

In the years leading up to 2025, despite economic interdependence and shared ASEAN commitments, unresolved demarcation issues, local militarization of border areas, and historical mistrust laid the groundwork for renewed confrontations. The combination of resource competition, strategic concerns over cross-border infrastructure, and nationalist rhetoric meant that any triggering incident could reignite tensions setting the stage for the latest conflict.

Recent Developments Leading to the 2025 Escalation

The renewed flare-up in 2025 can be traced to a combination of political, security, and resource-related triggers that gradually intensified over the preceding months.
Firstly, nationalist rhetoric on both sides gained momentum, with political leaders in Thailand and Cambodia facing domestic pressures to project a firm stance on sovereignty. Cambodian officials, under scrutiny for perceived concessions in earlier negotiations, began reinforcing their claims through both legal references and symbolic acts such as commemorations at the Preah Vihear Temple. In Thailand, opposition groups criticized the government for “weak border policy,” compelling Bangkok to adopt a more assertive posture.

Secondly, the completion of new road and infrastructure projects near the disputed areas partly funded by foreign investment heightened concerns over de facto territorial control. These developments not only brought more troops and civilians into proximity but also increased the economic stakes for both governments. Reports of road extensions linking to military outposts fueled accusations of strategic encroachment.

Thirdly, sporadic skirmishes between patrol units throughout late 2024 escalated tensions. Incidents included the destruction of temporary border markers, detentions of villagers accused of trespassing and artillery fire during a disputed clearing operation. Social media further amplified the situation, with viral images of troop movements sparking nationalist sentiment and public outrage in both nations.

By early 2025, diplomatic channels had visibly strained. Joint border committee meetings stalled over disagreements on demarcation maps, while backchannel talks failed to prevent the deployment of additional military units on both sides. The combination of domestic politics, contested infrastructure expansion, and persistent low-level clashes created a volatile environment ultimately tipping the dispute into its most serious phase since the early 2010s.

Root Causes of the Conflict

The July 2025 outbreak did not arise from a single mistake or momentary lapse; it was the violent expression of layered and long-embedded causes. At the most basic level, the dispute is a product of ambiguous colonial-era border-making. The Franco–Siamese treaties of the early 20th century and the maps produced by French cartographers left several border segments poorly defined most notably the area around the Preah Vihear temple and adjacent promontory. Although the International Court of Justice (ICJ) ruled in 1962 that the temple itself lay within Cambodian territory, the court’s decision left adjacent tracts of land unclear. Those legal ambiguities created a recurring gray zone where patrols, roads, and development projects repeatedly collided with competing claims, enabling localized incidents to escalate rapidly.

Cultural and identity claims amplify the raw territorial dispute and make compromise politically costly. Preah Vihear is not merely a piece of land: it is a potent national symbol. Cambodia sees the temple as a tangible inheritance of the Khmer Empire and a vindication of national sovereignty. Thailand, meanwhile, has communities and nationalist narratives that consider parts of the same cultural landscape as historically linked to Thai heritage. The UNESCO listing of Preah Vihear in 2008 crystallized these tensions what for Cambodia was a cultural recognition was viewed by many in Thailand as an encroachment on territory. This symbolic salience means that governments find it difficult to offer concessions without risking domestic blowback, turning a border question into a test of national honour.

Domestic politics in both capitals have repeatedly served as accelerants. In Thailand, the balance between civilian governments, royal prerogatives, and a politically powerful military creates frequent spikes of instability; leaders have at times used assertive foreign-policy gestures to consolidate support or to distract from internal troubles. The 2025 crisis occurred against this combustible backdrop: the political fallout from a leaked phone call between Thailand’s Paetongtarn Shinawatra and Cambodia’s Hun Sen (a figure of outsized influence) inflamed public opinion and strengthened military and nationalist voices that favoured a hard line. Cambodia’s leadership, likewise, has leveraged territorial defence as a means of consolidating domestic legitimacy; the Hun family’s continued prominence in Cambodian politics has made a firm stance on sovereignty both a personal and political imperative.

Security dynamics and militarization along the frontier converted political disputes into kinetic danger. Both states increased troop deployments, hardened positions, and improved outposts on the Dangrek escarpment and surrounding high ground the very terrain that confers tactical advantage. Landmines and unexploded ordnance from past conflicts litter the borderlands, raising the odds that patrols or civilian movements will trigger new violence. That danger was tragically realized in 2025: a landmine incident and subsequent exchanges in late July spiralled into five days of fighting that left dozens dead (at least 38 by official tallies used in this article) and displaced hundreds of thousands. Once artillery, mortars, and rockets enter a contest, the humanitarian cost multiplies rapidly, and local incidents become national crises.

Failures of diplomacy and institutional mechanisms also played a central role. ASEAN’s consensus-based, non-interference model has limited capacity to act decisively when two member states clash and bilateral border committees where progress could be made had stalled or produced little in the months before the outbreak. Cambodia repeatedly turned to international legal remedies (the ICJ) for clarification, while Thailand has consistently preferred bilateral negotiation and has at times rejected the Court’s jurisdiction for further demarcation. This mismatch one side seeking third-party arbitration, the other insisting on direct talks meant that no mutually trusted mechanism existed to defuse disputes before they turned violent.

External geopolitics complicated the picture rather than simplifying it. Closer Cambodian ties with China and Thailand’s security relationships and trade links with other powers introduced an extra dimension of influence and pressure, which domestic actors exploited. In 2025, international actors most visibly Malaysia as mediator and the United States through intense economic pressure helped secure a ceasefire, but their involvement also revealed how quickly outside leverage can alter incentives without resolving the underlying boundary questions.

Finally, the information environment social media, nationalist media outlets, and targeted disinformation fanned mistrusts and hardened public attitudes on both sides. Viral clips, selective leaks (such as the phone audio), and inflammatory commentary raised the political cost of compromise and made measured diplomacy harder to sell to domestic audiences.

Combined, these factors ambiguous colonial borders, symbolic attachment to territory, domestic political imperatives, militarization of the frontier, stalled diplomatic channels, external strategic competition, and a combustible information environment created a tinderbox. The May–July 2025 incidents provided the spark; the structural drivers ensured the spark would ignite into the worst confrontation in over a decade. Without addressing the legal ambiguities, building durable confidence-building measures, and creating credible, mutually acceptable dispute-resolution processes, the border is likely to remain a recurring flashpoint.

Conclusion

The July 2025 ceasefire between Thailand and Cambodia marks a rare moment of reprieve in a dispute defined by decades of mistrust, unresolved territorial questions, and cycles of confrontation. It has halted the most intense border fighting in over a decade and created a fragile space for diplomacy to work. Yet, the durability of this pause in hostilities will depend not only on immediate military disengagement but also on the political will of both governments to transform a temporary truce into a sustainable peace.

To succeed, Bangkok and Phnom Penh must move beyond crisis management and invest in confidence-building measures such as troop withdrawals from contested zones, coordinated border patrols, and permanent communication hotlines that reduce the risk of accidental escalation. Expanding cross-border economic, cultural, and tourism ties could help replace zero-sum rivalry with mutual benefit, softening the political cost of compromise.

The risks, however, remain acute. Domestic political volatility in either country could reignite nationalist fervor, turning the border dispute into a tool of internal political mobilization. If the demarcation process continues to stall and neither side shows flexibility, trust will erode, making renewed clashes more likely.

At the regional level, ASEAN’s role bolstered by possible ICJ oversight could prove decisive in steering the conflict toward a formal, mutually recognized settlement. Success would not only resolve one of Southeast Asia’s most persistent flashpoints but also enhance ASEAN’s standing as a credible mediator. Failure, by contrast, risks cementing a “frozen conflict,” where fighting subsides but the underlying dispute remains unresolved, ready to flare whenever political winds shift.

For now, the ceasefire is a doorway, not a destination. Whether it leads to lasting peace or back to the trenches will hinge on what happens in the weeks and months ahead.

About the Author

Megha Mittal is a scholar of International Relations with an academic foundation in Spanish language studies. Her work engages with the study of geopolitics, foreign policy, and global governance, reflecting a broad interest in the dynamics that define and influence international affairs.

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