Thailand was set for an earlier than expected election after its king endorsed Prime Minister Anutin Charnvirakul's bid to dissolve parliament on Friday, as a border conflict with Cambodia raged and the government moved to head off a no-confidence vote.

Anutin late on Thursday announced he was "returning power to the people", and King Maha Vajiralongkorn approved his petition to dissolve the house, according to a royal gazette posting overnight, paving the way for an election as early as February.

Anutin's play comes as an armed border conflict between Thailand and Cambodia entered into a fifth day, with at least 20 people killed, close to 200 wounded and hundreds of thousands of people displaced.

Late on Thursday, US President Donald Trump, who intervened in July the last time fighting erupted, reiterated his plan to call leaders of both countries and try to end the conflict.

Cycle of political drama

Anutin's decision to dissolve the house came less than 100 days after he was sworn in as head of a minority government, and occurred amid high drama in parliament that raised expectations that the opposition People's Party, the biggest force in the house, would file a no-confidence motion against him.

The election, which must take place within 45 to 60 days, raises the spectre of even more political turmoil in Thailand, which for the past two decades has seen multiple elected governments and parties brought down by coups and court rulings in an intractable power struggle involving rival elites and progressive forces.

Anutin was elected prime minister by parliament in September after a court removed Paetongtarn Shinawatra from office, with his rise only possible due to a deal he struck with the People's Party to back him, on the condition that he starts the process of amending the constitution and then dissolves the house in late January.

But chaos ensued in a joint sitting of the legislature on Thursday over the voting process to amend the constitution. Opposition leader Natthaphong Ruengpanyawut said Anutin's party had reneged on an agreement and a government spokesperson said a no-confidence motion was being planned.

Electoral challenge for Anutin

Anutin, an astute political deal-maker and Thailand's third prime minister in two years, faces an uphill struggle to be re-elected, with opinion polls consistently showing the liberal opposition to be the country's most popular party.

A forerunner to the People's Party won the 2023 election on an anti-establishment platform but was blocked from forming a government by lawmakers allied with the royalist military.

Anutin on Friday told reporters his decision to dissolve parliament would not affect management of the conflict with Cambodia and government spokesman Siripong Angkasakulkiat told Nation TV the caretaker administration has "full authority".