Senator Upakit Pachariyangkun on Monday attended a preliminary hearing involving a 100-million-baht defamation lawsuit he filed against Move Forward Party MP Rangsiman Rome.
The lawsuit was lodged after the general debate in February in which Mr Rangsiman raised money laundering allegations against a senator with the Thai initial "Or".
Then Mr Upakit had his lawyer file a defamation lawsuit against Mr Rangsiman seeking 100 million baht in damages. The Criminal Court scheduled the preliminary hearing on Monday before determining if the lawsuit would be accepted. It was reportedly postponed from May 1.
The MFP MP insisted on Monday he was doing his job when he raised alleged irregularities involving the senator during the general debate.
Mr Rangsiman said there had been several developments involving the senator after the general debate, which he felt the need to discuss publicly.
"I'll fight the cases against me, and I'm confident I'll win," he said.
Mr Rangsiman's legal team said the court would review the plaintiff's witness testimony to determine if there are grounds for the allegations.
Mr Upakit, who was greeted by a group of supporters, said on Monday two witnesses, including himself, would give statements to the court.
The senator was recently charged with colluding in money laundering and involvement in a transnational criminal organisation while serving in the upper chamber.
He strongly denied 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.
The attorney-general will decide on the matter on July 26.
