The Election Commission (EC) is being asked to investigate if property tycoon Srettha Thavisin, a key Pheu Thai Party figure, broke election rules when he told people to accept vote-buying money during a recent campaign rally.
Sonthiya Sawasdee, a former adviser to the House committee on law, justice and human rights, submitted the petition to the EC on Tuesday, seeking a probe of Mr Srettha's speech at a Pheu Thai rally in Phichit province on Saturday.
Mr Srettha serves as an adviser to Paetongtarn Shinawatra, Pheu Thai's chief adviser on public participation and innovation and head of the "Pheu Thai Family".
He is also widely speculated to be one of the party's prime minister candidates.
In his complaint to the EC, Mr Sonthiya said Mr Srettha told the rally attendants to accept vote-buying money regardless of political parties and candidates they intended to vote for.
He quoted the property tycoon saying, "If cash is handed out [to buy votes], take it whether or not you will vote for them. Pheu Thai mainly focuses on policy."
According to Mr Sonthiya, such remarks are deemed to undermine clean and fair elections.
He also said thousands of people joining the Pheu Thai rally last Saturday wore red shirts with the same political slogan, and the EC should examine if they were promised money or already paid to do so.
Mr Sonthiya also submitted opinions of academics to support his March 7 petition seeking the dissolution of the Pheu Thai Party for allowing Nattawut Saikuar, a non-member, to dominate party affairs.
He said Mr Nattawut is serving a political ban and therefore cannot engage in politics, but the party has appointed him as the Pheu Thai Family director, which puts him in a canvasser role.
Mr Nattawut's behaviour is a violation of the charter, and Pheu Thai has broken sections 28 and 29 of the Political Party Act in this regard, Mr Sonthiya claims.
Section 28 prohibits a political party from letting an outsider control, influence or guide its activities in a way that affects the independence of the party and its members.
Section 29 bars a non-party member from dominating, influencing or directing party affairs, both directly and indirectly, to limit party members' freedom.