Pol Col Thawee Sodsong, the Prachachat Party secretary-general and list MP, has been elected as the new leader of the party, succeeding Wan Muhamad Noor Matha.
Mr Wan resigned as leader of the Prachachat Party after he was appointed speaker of the House of Representatives.
The party held a general assembly at the Yala Rajabhat University in Yala province on Saturday to elect Mr Wan's successor and the new party executive committee.
The meeting, chaired by acting party leader Worawi Makudi, was attended by about 1,000 party members.
Pol Col Thawee, the party secretary-general, was elected the new party leader.
At the meeting, Pol Col Thawee declined to comment on a report that he had been tipped to take the post of justice minister in the coalition government led by the Pheu Thai Party, saying that this had yet to be confirmed.
He also declined to comment on public criticism that former prime minister Thaksin Shinawatra had been given favourable treatment in jail after returning to Thailand.
Pol Col Thawee said he had not yet looked into this matter in detail as the new government had yet to take office and the Justice Ministry is still being overseen by out-going Deputy Prime Ministe Wissanu Krea-ngam.