Future Forward members on Monday voted overwhelmingly to expel four MPs who have continually voted against the party in parliament.
A general meeting voted 250-5 to axe MP for Chiang Mai Srinuan Boonlue, MP for Chon Buri Kawinnart Takee and two MPs representing Chanthaburi province, Charuek Sri-on and Pol Lt Col Thanapat Kittiwongsa.
Deputy party spokesman Natcha Boonchaiinsawat said the decision will be forwarded to the party executive for a stamp of approval. The renegade members will then have 30 days in which to join a new party, or lose their seats.
The four had each failed to support the party's position in the House on more than one occasion, and some also opposed the party's call for a rally on Saturday, he said.
He did not identify the MPs who opposed the rally.
Ms Srinuan abstained in the vote on an executive degree to transfer army units to the royal command in October. She gained more votes than any other constituency MP in the House, winning her seat for the Future Forward Party in a by-election in Chiang Mai on May 26 with about 75,000 votes.
She said on Friday that she was ready to walk away from the party and felt no guilt.
Pol Lt Col Thanapat also broke with his party and voted for the executive decree, while Mr Kawinnart twice voted against the party in parliament -- in favour of the army unit transfer decree, and the government's 3.2-trillion-baht spending budget for the 2020 fiscal year.
Mr Charuek also voted for the executive decree.