When weeks of tensions escalated into a major border conflict with Thailand last week, former Cambodian Prime Minister Hun Sen appeared to take charge of his country’s response.

Photographs showed him at the end of a long table, speaking with military officers and poring over detailed maps, radio set in hand and a cup of Starbucks coffee within arms reach.

The former guerrilla fighter is no longer Cambodia’s leader, having passed on the premiership to his eldest son in 2023 after nearly four decades in power, and has taken over as the president of the Southeast Asian nation’s Senate.

But Hun Sen played an outsized role in events leading up to the deadliest fighting between Thailand and Cambodia in over a decade and - according to three diplomatic sources - showed his continuing influence during the five-day conflict.

On Friday, after artillery fired from Cambodia landed in civilian areas in Thailand’s border provinces, the Thai army took direct aim at him.

“Based on available evidence, it is believed that the Cambodian government, led by Samdech Akka Moha Sena Padei Techo Hun Sen, is behind these appalling attacks,” it said in a statement, using honorifics for the veteran politician.

Within hours of the clashes breaking out, Hun Sen, 72, was sharing a flurry of posts on Facebook, his favoured social media platform, to rally his people and criticise Thailand.

In one photograph he posted, Hun Sen is seen in a video conference call with a dozen people, including several soldiers. In another post, he shared a photo of himself in combat fatigues.

“On the border clashes, what strikes me is the extent to which he goes to create the optics of being in charge - wearing the uniform, being seen as directing the troop movements, intervening on Facebook,” a Cambodia-based diplomat told Reuters.

Like all the other diplomats interviewed for this story, he asked not to be named because of the sensitivity of the issue.

Lim Menghour, a Cambodia government official working on foreign policy, said Hun Sen acted as the main logistics commander for troops on the frontline.

“He has always monitored and kept observing the situation all the time,” he told Reuters.

Leaked call and crisis

In contrast to his father, Cambodia’s incumbent premier Hun Manet, a four-star general and graduate of the West Point military academy in the United States, remained more muted on social media in the early days of the conflict, changing tack as he readied to travel to Malaysia for negotiations that yielded a ceasefire.

Chhay Sophal, a Phnom Penh-based author of books on Hun Sen and his family, said the former premier can direct the government in his capacity as the president of the ruling Cambodian People’s Party.

“So, the prime minister must respect and follow the party’s policy and president,” he said.

A Cambodia government spokesman did not respond to questions from Reuters.

Thailand and Cambodia have bickered for decades over undemarcated sections of their 817 km (508 miles) land border, which has also led to fighting in the past.

The recent tensions began rising in May, following the killing of a Cambodian soldier during a skirmish, and have steadily escalated since - a situation that Thai premier Paetongtarn Shinawatra sought to diffuse when she spoke directly with Hun Sen on June 15.

A partial recording of the call was initially leaked, where Paetongtarn, 38, can be heard criticising a Thai general and kowtowing to Hun Sen, who later released the full audio of their conversation, triggering a political crisis in Thailand.

In a rambling three-hour televised speech in late June, Hun Sen openly rebuked Paetongtarn for her handling of the border row and attacked her father, former premier Thaksin Shinawatra, long seen as his ally.

“At least before the flare-up, he was very much right there in your face,” said a regional diplomat who closely tracks Cambodia.

“I mean, he was the one who was mostly visible, who was making all the pronouncements.”

Rice fields to power

Hun Sen is a wily survivor of Cambodian politics and the wider tumult across Southeast Asia over the last half-a-century.

Born to rice farmers in a province heavily bombed during the secret US war in Cambodia and Laos, he became a soldier for the Khmer Rouge, whose murderous regime from 1975 to 1979 killed about a quarter of the population.

But he defected to Vietnam in 1977 and, when they overthrew the Khmer Rouge, Hun Sen returned as foreign minister and then rose to become prime minister.

The self-styled strongman presided over an economic boom in Cambodia, with per capita income almost quadrupling from $240 to $1,000 in the decade from 1993 to 2013.

But much of the new-found wealth came to be concentrated in the hands of the country’s ruling elite, even as political rivals were jailed or exiled, critical media outlets shuttered and civil dissent crushed, paving the way for Hun Manet to take over.

In recent months, even domestic administrative policy decisions were being brought to Hun Sen for approval, according to the regional diplomat who interacts with Cambodian officials.

Now, the border conflict has made his clout more apparent, and there has been an outpouring of support for the government on social media amid a wave of nationalism.

“It hasn’t surprised anyone that he’s taken the lead which tells you everyone knew he was in charge,” another Cambodia-based diplomat said.

“If the goal is to strengthen nationalism, he has succeeded.”