The main opposition Pheu Thai Party denies that ex-prime minister Thaksin Shinawatra has wielded influence over the party just as activist Srisuwan Janya is set to ask the Election Commission (EC) to look into the matter on Wednesday.
If the claim is proven, the party stands to be dissolved for violation of the political parties law.
The move comes after Thaksin, now in self-imposed exile overseas, had written to ask voters in Chiang Mai to support Pheu Thai candidate Pichai Lertpongadisorn in the Provincial Administrative Organisation (PAO) chairman election on Dec 20.
Mr Srisuwan, secretary-general of the Association for the Protection of the Thai Constitution, said on Tuesday that he will on Wednesday ask the EC to investigate whether Pheu Thai had allowed Thaksin, who is not a Pheu Thai member, to dominate or control it in violation of the political parties law.
If the EC finds grounds to the accusation, it will take the case to the Constitutional Court. If found guilty, the party will be dissolved, Mr Srisuwan said.
Pheu Thai deputy leader Chusak Sirinil dismissed the claim that the party is under the influence of Thaksin. Mr Chusak said that regulations over the PAO elections do allow outsiders to help with election campaigns.
"The constitution also permits those who have voting rights to help election candidates campaign. Also, Thaksin did not mention Pheu Thai. In his letter, he merely expressed his personal opinions and did not force the party to help with the campaigns," Mr Chusak said.
Pheu Thai MP for Maha Sarakham Sutin Klungsang said that the political parties law prohibits outsiders from wielding influence in running a political party, but the fact that Thaksin wrote a letter to Chiang Mai voters had nothing to do with the management of party affairs.
It was a personal matter for Thaksin to support an election candidate and communicate this to people, Mr Sutin said.
Thaksin's endorsement of Mr Pichai in the PAO chairman poll in Chiang Mai came on the heels of a conflict between Pheu Thai and Jatuporn Promphan, chairman of the red-shirt United Front for Democracy against Dictatorship (UDD).
Mr Jatuporn recently lambasted Pheu Thai over its selection of candidates ahead of the Dec 20 PAO chairman election. Speaking during the UDD-sponsored Peace Talk, he accused Pheu Thai of abandoning Boonlert Buranupakorn, leader of the Chiang Mai Khunnatham group and of falsely accusing Mr Boonlert of siding with the rival ruling Palang Pracharath Party. He also alleged that Yaowapa Wongsawat, Thaksin's younger sister, excluded Mr Boonlert from the PAO chief race.