People's Reform Party leader Paiboon Nititawan said on Thursday he will join the Palang Pracharath Party (PPRP) after the closure of his own party becomes official.
The People's Reform Party applied for closure with the Election Commission (EC) on Aug 5, explaiining that its executive members were preoccupied with other engagements.
Mr Paiboon, who is the party's only MP, on Thursday declared his decision to join the PPRP after his party's shutdown is officially printed in the Royal Gazette.
A staunch supporter of Prime Minister Prayut Chan-o-cha since the coup in 2014, he had discussed his political future with Deputy Prime Minister Prawit Wongsuwon - a move that will lift the number of PPRP seats to 117.
Mr Paiboon said the People's Reform Party and PPRP shared the same political ideology.
The constitution gives MPs 60 days to find a new party is their party is officially disbanded or closed.
However, former EC commissioner Somchai Srisutthiyakorn warned of the possibility of Mr Paiboon being unseated from parliament due to the new election formula, which requires people cast votes for constituency MPs and party-list MPs on the same ballot paper.
Voters cast ballots for the People's Reform Party in the March general election, he said on his Facebook account. The poll agency might have to recalculate the party list-MP seat allocation, by excluding votes for Mr Paiboon's party.