About 40 politicians, 34 of them former MPs, applied for membership of Bhumjaithai on Friday, confirming their intention to run under their new party's banner at the coming general election.
They converged at Bhumjaithai headquarters and were officially introduced on stage by party registrar Supachai Jaisamut.
They included 11 former MPs of the Palang Pracharath Party (PPRP), seven from Pheu Thai, five from Move Forward and one former Democrat. All had resigned from their House seats.
Surprising new members included Sihadet Kraikupt. He is the elder brother of Pareena Kraikupt, who is a former PPRP MP for Ratchaburi and strong supporter of Prime Minister Prayut Chan-o-cha and Prawit Wongsuwon, the deputy prime minister and PPRP leader.
Ms Pareena said her respect for Gen Prawit was unchanged. Her brother had made his own decision to run with Bhumjaithai.
PPRP has reportedly decided not to field her brother as a candidate in the elections scheduled by May next year, despite her strong ties with the ruling party.
"Give my brother a chance," she said, expressing confidence that Mr Sihadet would emerge a winner.
Ms Pareena was banned from politics for life by the Supreme Court for illegal occupation and use of land in a forest reserve in her home province of Ratchaburi.
The mass defection of former MPs from other parties to Bhumjaithai will strengthen the chances of party leader Anutin Charnvirakul, the current health minister, becoming prime minister after the polls.
Mr Anutin's only comment was that all these new members would make the party stronger as it prepares for the general election.