Thousands of anti-government protesters gathered in Thailand’s capital on Saturday demanding Prime Minister Paetongtarn Shinawatra’s resignation following a leaked diplomatic phone call.

A Cambodian elder statesman leaked a call meant to soothe a border spat between the two nations in which Paetongtarn called him “uncle” and referred to a Thai military commander as her “opponent”.

A key party abandoned Paetongtarn’s coalition, accusing the 38-year-old dynastic premier of kowtowing to Cambodia and undermining Thailand’s military, leaving her teetering with a slim parliamentary majority.

About 10,000 demonstrators jammed roads ringing the capital’s Victory Monument, waving Thai flags and placards reading “Evil PM, get out”.

One speaker took to the stage and shouted: “PM, you committed treason!”

The crowd was mostly senior-aged and led by veteran activists of the “Yellow Shirt” movement, which helped oust Paetongtarn’s father Thaksin in the 2000s.

One of Thaksin’s former allies, now among his harshest critics, was also a key organizer.

“I’m here to protect Thailand’s sovereignty and to say the PM is unfit,” said 70-year-old protester Seri Sawangmue, who travelled overnight by bus from the country’s north to attend.

“After I heard the leaked call I knew I couldn’t trust her,” he told AFP. “I’ve lived through many political crises and I know where this is going. She’s willing to give up our sovereignty.”

Thailand has seen decades of clashes between the bitterly opposed “Yellow Shirts” who defend the monarchy and military, and the Thaksin-backing “Red Shirts”, considered by their opponents a threat to the traditional social order.

Jamnong Kalana, 64, said she was once a “Red Shirt” but had changed her colours and was demanding the resignation of Paetongtarn, leader of the Pheu Thai party.

“I feel full of pain when I see a fellow Thai who doesn’t love the country like I do,” she said.

Make-or-break court cases

Mass protests have been uncommon in Thailand since 2021, when youth-driven demonstrations calling for monarchy reform ended with many leaders convicted under the country’s strict lese-majeste laws.

Authorities said more than 1,000 police and 100 city officials had been deployed to the protest, which remained peaceful on Saturday afternoon.

The 62-year-old protester Santhiphum Iamjit was overcome with emotion.

“Our ancestors shed blood, sweat and tears for this land, but now politicians are ready to give it away for personal gain,” the former bureaucrat tearfully told AFP.

Paetongtarn was visiting Thailand’s flood-hit north but before departing Bangkok she told reporters: “It’s their right to protest, as long as it’s peaceful.”

The prime minister has been battered by controversy and abandoned by her largest backer, the Bhumjaithai Party, after her phone call with Cambodia’s ex-leader Hun Sen was leaked earlier this month.

Tensions between the countries have soared after a border dispute boiled over into violence last month which killed one Cambodia soldier.

Thailand’s military has staged a dozen coups since the end of absolute monarchy in 1932 and politicians are usually careful not to antagonise the generals.

After calling a border region military commander her “opponent”, Paetongtarn gave a contrite press conference where she issued a public apology flanked by military officials in a show of unity.

Her remaining coalition partners have not yet backed out of their pact.

But next week both Paetongtarn and her father face legal battles that could reshape Thailand’s political landscape.

On Tuesday the Constitutional Court will decide whether to take up a petition by senators seeking her removal over alleged unprofessionalism.

That same day her father is set to stand trial on royal defamation charges linked to decade-old remarks to South Korean media.

Paetongtarn took office less than a year ago after her predecessor was disqualified by a court order and her father returned from exile after 15 years.

She is the fourth Shinawatra-linked figure to become prime minister following her father, aunt and uncle-in-law.