Pita Limjaroenrat has resigned as leader of the Move Forward Party (MFP) to make way for his successor to take up the post of opposition leader.
Mr Pita, who has been included on the TIME100 Next list of young global leaders to watch, conveyed his resignation message via his Facebook page on Friday, addressing it to all MFP members and the general public.
In his message, Mr Pita said that while the MFP boasts the largest number of MPs within the opposition bloc, he cannot accept the position of opposition leader due to his suspension by the Constitutional Court from performing his duties as an MP.
"The current constitution stipulates that the opposition leader must be an MP who leads the top opposition party, but I am still unable to fulfill my duties in the House of Representatives and won't be able to accept the role of opposition leader in the near future.
"After consulting with the executive committee and party MPs, we have concluded that the position of 'opposition leader' is of utmost importance in the parliamentary system, and the position should be undertaken by the main opposition party in the House of Representatives.
"In other words, the MFP should lead the opposition, which is responsible for keeping the government under scrutiny and checks and pushing for changes that are not included in the government's policies.
"I have decided to step down from my position as the MFP leader, allowing the party to select an MP capable of assuming the role of 'opposition leader' to replace me as party leader."
The 43-year-old alumnus of Harvard Kennedy School of Government said that despite his resignation, he would still work for the MFP and the people to the best of his ability.
He called for all MFP members to gather at the Keelawes Building 1 in Bangkok's Din Daeng area on Sept 24 to elect the new party leader.
Observers have speculated that Chaithawat Tulathon, the party secretary-general, is the likely successor to Mr Pita.
Move Forward Party secretary-general Chaithawat Tulathon. (Photo: Chanat Katanyu)