Mingkwan Sangsuwan, former leader of the New Economics Party (NEP), who officially joined the ruling Palang Pracharath Party (PPRP) on Tuesday, is expected to be named one of its prime ministerial candidates.
He was warmly welcomed by PPRP leader Prawit Wongsuwon and other key party figures.
Speaking after being unveiled as a new PPRP member, Mr Mingkwan said he decided to switch parties because he was asked to help out with economic affairs, his area of expertise.
He noted that he had no interest in joining the party's management or executive committee.
However, Mr Mingkwan said he intended to represent the PPRP in policy debates during the election campaign, and had discussed this with the PPRP leader.
He said Gen Prawit had suggested he may need to hold a certain post to participate in such debates because in the previous general election, only a party leader and prime ministerial candidates could join them.
"Gen Prawit told me he would ask the party to consider naming me as one of its prime ministerial candidates. He told me the matter would be brought before the party," he said.
Gen Prawit was seen nodding in response to Mr Mingkwan's remark about him likely being nominated as a candidate.
"I'm really sorry to mention Gen Prayut today. He is no longer in the party. I just got this information around noon. I don't have any problem with Gen Prayut and I hold no grudge against him, even when I grilled him during the House debates," he said.
When asked if the PPRP would name Gen Prayut as one of its prime ministerial candidates, Gen Prawit said: "Gen Prayut is gone. He has left. Khun Mingkwan just said so."