Thai royal officials rejected a request by the ruling party to dissolve parliament, the country's acting prime minister said on Thursday, clearing the way for a vote that could select his successor.

A power vacuum has consumed Thailand's top office since Friday, when the Constitutional Court sacked prime minister Paetongtarn Shinawatra over an ethics breach.

A coalition of opposition MPs has backed conservative construction magnate Anutin Charnvirakul to take the top office, with a vote scheduled for Friday at around 10am.

Paetongtarn's Pheu Thai party – still governing in a caretaking capacity – had attempted to dissolve the legislature and block the vote, submitting its request to the palace.

But caretaker premier Phumtham Wechayachai said the Office of the Privy Council told him it was "inappropriate to present the draft of the royal decree to his majesty at this time".

The office told him there were "disputed legal issues" over his authority to dissolve parliament in a caretaker capacity, he said in a message on Facebook.

The path is now clear for MPs to vote for a new leader.

Anutin, 58, has previously served as deputy prime minister, interior minister and health minister – but is perhaps most famous for delivering on a promise in 2022 to legalise cannabis.

Pheu Thai has been a dominant force in Thai politics for the past two decades, cultivating a populist brand which has jousted with the pro-military, pro-monarchy establishment.

Paetongtarn's sacking dealt another heavy blow to the Shinawatra dynasty, increasingly bedevilled by legal and political setbacks.

Anutin once backed Paetongtarn's coalition but abandoned it over her conduct in the border row with Cambodia that resulted in her ouster last week.

He has managed to secure the crucial backing of the 143-seat People's Party, which is in opposition despite holding the most seats in parliament.

Anutin's Bhumjaithai Party is the third largest, so he would look likely to secure a comfortable majority with support from a smattering of other allies.

However, the People's Party has said it will not join his cabinet, and has made its support conditional on parliament being dissolved for fresh elections within four months.

Pheu Thai announced it had entered his request to dissolve parliament just moments after the People's Party backed their rival. (AFP)