BANGKOK: Thailand's election-winning Move Forward Party has been excluded from a coalition of parties hoping to form the next government after a May general election, parties in the alliance said on Wednesday.

Southeast Asia's second largest economy has been in political limbo since the poll, in which the progressive Move Forward emerged as the largest party, closely followed by the populist Pheu Thai party.

Pheu Thai, the latest incarnation of a party founded by former telecoms tycoon Thaksin Shinawatra, said it would nominate a businessman, Srettha Thavisin, in a parliamentary vote for prime minister, due on Friday, and it aimed to form a government without Move Forward.

"Pheu Thai, in consultation with Move Forward, will withdraw from cooperation and will move ahead with government formation and nominating Srettha Thavisin for prime minister," the Pheu Thai party said.

A Move Forward spokesperson said the party would comment after its lawmakers met later on Wednesday.

Move Forward took the lead in efforts to form the next government after the May 14 election, in which many voters rejected more than a decade of rule by the military and a military-backed government.

But twice its attempt to get its leader, Pita Limjaroenrat, voted in as prime minister by parliament were blocked by conservative opponents and a military-appointed upper house Senate.

Conservative opposition to Move Forward stemmed from its progressive agenda that was seen by the royalist-military establishment as a threat, in particular a promise to amend a law, known as article 112, that punishes insulting the monarchy with prison of up to 15 years.

Pheu Thai deputy leader Phumtham Wechayachai said a government led by his party would not support amending article 112 but would focus on solving economic and political problems.

Another Pheu Thai leader, Chonlanan Srikaew, told a press conference in Bangkok his party had little choice but to break with its ally in the face of insurmountable conservative opposition to it.

"Pheu Thai has supported Move Forward to our fullest ability," Chonlanan said.

Move Forward rose to prominence with the backing of many younger voters who protested for months against a military-backed government in 2020.

On Wednesday, several hundred supporters of Move Forward assembled in Bangkok in cars and on motorbikes for a noisy show of opposition to the party's exclusion from efforts to form the next government.

The combined two houses of parliament are due to vote for a new prime minister on Friday.