Move Forward Party spokesman Rangsiman Rome will on Thursday submit a petition to the National Anti-Corruption Commission (NACC) seeking a probe into an alleged false declaration of assets by Senator Upakit Pachariyangkul.
The politician earlier accused the appointed senator of having made the false declaration upon assuming his post, zeroing in on the sale of a hotel business worth US$8.15 million (280.1 million baht) in Myanmar's Tachilek.
Speaking at a press conference, Mr Rangsiman said he would ask the anti-graft agency on Thursday to investigate the senator's assets with the focus on the sale of the hotel in question.
The NACC would also be asked to look into the revocation of the arrest warrant against the senator suspected of having links with drug trafficking rings and probe why bank accounts with alleged links to drug trade were not suspended, he said.
Mr Rangsiman also said his allegations against the senator were not politically motivated and surfaced while he was doing his job as an opposition MP.
Mr Upakit last week held a press conference to deny the allegations that he had connections with drug rings and laundered ill-gotten money through an electricity supply business operating on the Thai-Myanmar border.
Mr Uppakit also suggested that attempts to link him with Myanmar national Tun Min Latt, who was arrested on a drug-related charge last year, were part of a conspiracy to bring the case to public attention for political gain.
Asked about the senator's remark about the relationship between Pol Lt Gen Manapong Wongpiwat, an inspector attached to Phayathai police station, and a potential MFP candidate, the MFP politician said their relationship is not relevant at all.
But Mr Rangsiman confirmed Pol Lt Gen Manapong is a friend of the police husband of a potential MFP candidate in Bangkok.
Pol Lt Gen Manapong became the focus after a seven-page letter written by a police inspector circulated on social media detailing how police arrested Tun Min Latt.
During interrogation, the suspect implicated the senator and on Oct 3 last year, the Criminal Court approved an arrest warrant on charges related to drug trafficking and money laundering, according to the letter.