House speaker Yongyuth Tiyapairat -- an executive leader of the party that heads the country's ruling coalition -- was charged with vote buying in his northern province of Chiang Rai before last December's election.

The Supreme Court accepted the case last month from the state Election Commission, which earlier ruled that Yongyuth was guilty.

"I want to protect the honor of the institution (Parliament)," Yongyuth said, adding that he needed time to prepare to fight the case in court.

Yongyuth said in February that he was not guilty, and told reporters that he had been framed by "a group of policemen and soldiers who colluded" to get him disqualified.

The court also accepted a case against Yongyuth's sister, La-ong Tiyapairat, a member of Parliament from Chiang Rai province, for alleged electoral fraud.

A guilty verdict could lead to the dissolution of the People's Power Party, which heads the coalition government.

Thai election law states that if a senior member of a political party is found guilty of electoral crimes, the entire party could be disbanded if that person is found to have acted on its behalf.

If the Supreme Court upholds the commission's ruling, both Yongyuth and his sister would have to resign as members of Parliament.

The Constitutional Court would then decide whether to disband the People's Power Party.

Yongyuth is a former adviser to former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 coup. He also served as government spokesman and environment minister under Thaksin.