A long-standing but fragile relationship between Thailand and Cambodia has shattered dramatically, with violent consequences. What began as a localized incident has now spiraled into deadly clashes along their contested border.

The flashpoint came on Thursday, following the injury of five Thai soldiers in a landmine explosion a day earlier. The Thai government has since reported at least 15 deaths—mostly civilians—with more fighting continuing into Friday. Cambodian officials also confirmed civilian casualties on their side.

Border tensions are not new. The dense jungles between the two countries have long been disputed territory. Past skirmishes, like those in 2008 and 2011, resulted in dozens of fatalities but were swiftly defused through diplomatic channels. Just this past May, after a Cambodian soldier was killed, both sides appeared committed to preventing further escalation, holding high-level military talks.

So why has this flare-up spiraled so quickly?

The root of the current tension lies in political fallout. Last month, Cambodia’s influential former leader Hun Sen publicly released a private phone call with Thai Prime Minister Paetongtarn Shinawatra. In it, she addressed him as “uncle” and criticized a Thai military commander—remarks that sparked outrage at home. The leak led to her suspension and a petition in Thailand’s Constitutional Court seeking her removal.

The reasons behind Hun Sen’s move remain unclear. For years, his family had maintained a close alliance with the Shinawatras, dating back to Thaksin Shinawatra’s time in power. Thaksin’s opponents have long accused him of prioritizing Cambodia’s interests over Thailand’s due to this friendship.

The personal and political ties run deep. After a coup ousted Thaksin’s sister, Yingluck, in 2014, Hun Sen offered refuge to their allies. Yet that relationship also had a darker side: cross-border cooperation in the shadowy world of intelligence and repression.

In 2020, Thai activist Wanchalerm Satsaksit vanished in Cambodia, widely believed to have been abducted by Thai agents. And earlier this year, a Cambodian opposition figure was gunned down in Bangkok, an act critics say was another result of quiet coordination between the countries’ security forces.

Now, the release of the leaked phone call has turned former friends into fierce adversaries.

Trade between the two countries—once worth billions—has stalled. Thai police have launched investigations into prominent Cambodian business figures suspected of ties to organized crime and scam operations. And on the ground, military presence and tensions are growing.

Hun Sen, never one to shy away from bold political maneuvers, has further escalated the situation. He claims to possess documents that could implicate Thaksin in serious crimes—including lèse majesté, a grave offense in Thailand with severe prison sentences.

Thailand responded swiftly, expelling Cambodia’s ambassador and recalling its own—an unmistakable signal of deteriorating diplomacy.

Both sides now appear entrenched. In Cambodia, Prime Minister Hun Manet—Hun Sen’s son—lacks the authority or experience to steer the crisis. Meanwhile, Hun Sen himself seems determined to push forward.

In Thailand, the Shinawatra-backed coalition is struggling with economic stagnation and looming U.S. trade penalties. Showing weakness in the face of Cambodian provocation could be politically disastrous.

Cambodia faces its own economic pressures. The tourism sector has yet to recover from the pandemic, hindered further by fears of kidnapping and forced labor linked to the country’s scam centers. U.S. sanctions could hit Cambodia even harder.

Still, both Thaksin and Hun Sen are seasoned political operators. If anyone can find an off-ramp from this conflict, it is likely them—provided they are willing to put old loyalties and recent hostilities aside.

There’s also a question of whether ASEAN, the regional bloc, will step in. Its original mission was to prevent conflicts between member states, and it may yet play a role in de-escalating this crisis.

But the biggest mystery remains: why did Hun Sen ignite this fire? Was it retaliation for Thai pressure on scam operations? A reaction to Thailand’s possible plans to legalize gambling, which could hurt Cambodia’s casino industry? Or a calculated move by a political survivor to discard a weakening ally and stir nationalist fervor at home?