December 19, 2025
KUALA LUMPUR – The border conflict between Thailand and Cambodia has entered a dangerous new phase. What should have remained a containable skirmish has now collided with United States pressure, domestic insecurities, over-stretched verification regimes and, most ominously, ambitious military objectives emanating from Bangkok. US President Donald Trump may be publicly urging both sides to comply with the Kuala Lumpur Peace Accord, but Thailand’s shift in military doctrine suggests it is preparing for a long contest, not a short one.
The Thai military’s directive for full combat readiness is not simply a defensive reflex. It signals a deeper strategic calculus: the desire to degrade Cambodia’s long-term military capacity. This is a goal that exceeds the scope of the ceasefire agreements that Washington helped witness and which ASEAN attempted to stabilize.
The US now finds itself watching two Southeast Asian neighbors slipping into a conflict that neither seems fully able, or willing, to halt.
But Thailand’s ambitions cannot be divorced from geography, weather and operational realities. While the monsoon in northeast Cambodia between November and April 2026 will be dry, the southwest sector that has seen the involvement of the Thai navy is normally wet and rainy during May and October.
Given the unusual weather patterns along the 818-kilometer border that separates Thailand and Cambodia with two climates, Thailand has to be wary of the differences in weather patterns that may help some movements in the northeastern sector between November and April and a southwest sector, which is wetter between May and November.
Granted Thailand’s decision to hold a general election on Feb. 8, 2026, more consideration would have to be given to such seasonal variations when making any military advances.
Thus, the risk is not total war, but a long war of attrition, one punctuated by air raids, artillery exchanges and political brinkmanship at the border.
When Trump stood as witness to the October ceasefire in Kuala Lumpur, he believed he had secured a diplomatic win that reinforced US influence in mainland Southeast Asia. But the Thai-Cambodian conflict has returned with a speed that blindsided Washington. Trump’s recent statements urging both sides to “honor peace pacts” reflect frustration as much as resolve.
From Washington’s viewpoint, the credibility of US diplomacy is now intertwined with the behavior of both governments. But credibility cannot restrain a military that believes the strategic window has opened.
Thailand’s military planners know that Cambodia’s forward defenses are vulnerable. They also know that Thailand’s own political calendar, flood disasters in the south, and a looming election in March or April 2026, creates incentives to demonstrate strength.
Phnom Penh has chosen a restrained tone: deny mine placement, lament civilian deaths and reaffirm loyalty to the peace accord. But it is also reinforcing defensive positions and consolidating troop deployments in the border areas most exposed to Thai pressure.
Cambodia understands two dangers simultaneously. First, the US has just lifted a long-standing arms embargo, signaling a renewed willingness to engage. Appearing reckless could jeopardize that opening.
Second, Thailand’s full-combat-readiness directive is not temporary. It is part of a doctrine shift designed to impose strategic costs on Cambodia for years to come. Thus, Cambodia’s challenge is to avoid escalation without appearing weak. It must defend without provoking, resist without overreacting and engage without yielding.
This is a narrow diplomatic and military corridor, one that will become narrower as the Thai elections approach.
ASEAN’s observer teams, under the Kuala Lumpur peace accord, were never built for instant crisis management. Verification requires access, forensic sequencing, evidence preservation and joint inquiry cooperation.
Yet border clashes unfold within seconds. When accusations fly before evidence is gathered, impartial verification becomes irrelevant in the eyes of domestic audiences.
This is not ASEAN’s failure. It is the inherent mismatch between verification and escalation. No neutral mechanism can outpace artillery fire or prevent retaliatory airstrikes.
The region must accept a difficult truth: verification stabilizes peace only when the political will to wait for it exists. That will is currently in short supply in both Bangkok and Phnom Penh.
Thailand’s government faces a public battered by the worst southern floods in years. Hat Yai was submerged almost entirely, with disaster-management agencies overwhelmed.
A government under severe domestic pressure often seeks a stabilizing narrative. For Thailand’s coalition leaders, projecting decisiveness, even aggression, serves that narrative.
Cambodia’s pressures are different but equally potent. Hun Manet needs to consolidate political legitimacy while maintaining newly improved ties with Washington. If Cambodia bows too easily to Thai demands, the domestic backlash could be intense.
These internal dynamics ensure that neither side wants to concede first. Every concession becomes a vulnerability. Every pause becomes a political risk.
Trump’s scrutiny matters, but not enough to dictate the tempo or trajectory of the conflict. Thailand and Cambodia are not simply reacting to US pressure; they are navigating their own domestic imperatives and historical grievances.
If anything, Trump’s involvement risks creating a political paradox: If Thailand pulls back, it appears to be bending to US pressure. If Cambodia concedes, it appears to be intimidated by Washington’s shadow.
Neither is desirable for governments trying to project sovereignty. Thus, US scrutiny becomes an irritant rather than a constraint. The monsoon ensures that Thai forces will not attempt risky ground incursions. The weather is an operational veto.
The real danger is what happens after the monsoon ends. If Thailand maintains its ambition to weaken Cambodia’s defense capabilities, the dry-season window may become an opportunity for more aggressive maneuvers.
In the meantime, ASEAN must prepare for a long contest of wills, not a sudden peace. Trump may be watching, but he is not in full control until his forays into other conflicts around the world finish.