BANGKOK (AP) - Thousands rallied in Thailand's capital on Saturday to demand the resignation of Prime Minister Paetongtarn Shinawatra, part of the brewing political turmoil set off by a leaked phone call with former Cambodian Prime Minister Hun Sen.

Paetongtarn faces growing dissatisfaction over her handling of a recent border dispute with Cambodia involving an armed confrontation May 28. One Cambodian soldier was killed in a relatively small, contested area.

The recorded phone call with Hun Sen was at the heart of the demonstration Saturday and has set off a string of investigations in Thailand that could lead to Paetongtarn's removal.

Outrage over the call mostly revolved around Paetongtarn's comments toward an outspoken regional army commander and her perceived attempts to appease Hun Sen, the current Cambodian Senate president, to ease tensions at the border.

About 20,000 protesters joined the rally as of Saturday night, according to an estimate by the Bangkok police. Despite a downpour in the afternoon, they held national flags and placards around the Victory Monument in central Bangkok as speakers took turns blasting the government. The participants, many of whom came in the morning, chanted slogans, sang and danced to nationalist songs.

"From a heart of a Thai person, we've never had a prime minister who's so weak," said Tatchakorn Srisuwan, 47, a tour guide from Surat Thani province. "We don't want to invade anyone, but we want to say that we are Thai and we want to protect Thailand's sovereignty."

The rally ended peacefully at night with the protesters vowing to return if Paetongtarn and her government ignore their demands.

There were many familiar faces from a conservative, pro-royalist group known as Yellow Shirts. They are longtime foes of Paetongtarn's father, former Prime Minister Thaksin Shinawatra, who reportedly has a close relationship with Hun Sen and who was toppled in a military coup in 2006. Rallies organized by Yellow Shirts also helped oust the elected government of Thaksin's sister, Yingluck Shinawatra, in a 2014 coup.

Hun Sen responds

Hun Sen on Saturday said the action by the Thai army at the disputed area was a serious violation of Cambodia's sovereignty and territorial integrity, despite the country's goodwill in attempting to resolve the border issue.

"This poor Cambodia has suffered from foreign invasion, war and genocide, been surrounded and isolated and insulted in the past, but now Cambodia has risen on an equal face with other countries," Hun Sen told an audience of thousands at the 74th anniversary celebration of the founding of his long-ruling Cambodian People's Party in the capital, Phnom Penh.

There is a long history of territorial disputes between the countries. Thailand is still rattled by a 1962 International Court of Justice ruling that awarded Cambodia the disputed territory where the historic Preah Vihear temple stands. There were sporadic though serious clashes there in 2011. The ruling from the U.N. court was reaffirmed in 2013, when Yingluck was prime minister.

Political fracture and investigations

The scandal has broken Paetongtarn's fragile coalition government, costing her Pheu Thai Party the loss of its biggest partner, Bhumjaithai Party. Its departure left the 10-party coalition with 255 seats, just above the majority of the 500-seat house.

Paetongtarn also faces other investigations that could lead to her removal from office.

Sarote Phuengrampan, secretary-general of the Office of the National Anti-Corruption Commission, said Wednesday that his agency is investigating Paetongtarn for a serious breach of ethics over the Hun Sen phone call. He didn't give a possible timeline for a decision.

Reports said the Constitutional Court could decide as early as next week whether it will take a petition requesting Paetongtarn's removal because of the phone call, enabling the court to suspend her from duty pending an investigation. The prime minister said Tuesday that she's not worried and is ready to give evidence to support her case.

"It was clear from the phone call that I had nothing to gain from it, and I also didn't cause any damage to the country," she said.

The court last year removed her predecessor from Pheu Thai over a breach of ethics. Thailand's courts, especially the Constitutional Court, are considered a bulwark of the country's royalist establishment, which has used them and nominally independent state agencies such as the Election Commission to cripple or sink political opponents.

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By JINTAMAS SAKSORNCHAI Associated Press

Associated Press writer Sopheng Cheang in Phnom Penh, Cambodia contributed to this report.

Source: Courthouse News Service