The party said that Sereepisuth had already informed Parliament of his desire to quit as a party-list MP in the first week of August.
The party rejected speculation that his decision to quit was due to his failure to get a ministerial post in the Pheu Thai-led coalition. Sereepisuth reportedly told party members that as they had only one seat in the lower House, it was not sufficient to perform parliamentary duties effectively.
Sereepisuth stayed out of the process of distribution of Cabinet portfolios among the coalition members, the party said, adding that he merely wanted to facilitate the formation of a new government so as to move the country forward, the party said.
Sereepisuth would endeavour to advance national interests as that is his ideology, the party said.
Seri Ruam Thai said that Sereepisuth would work to verify the issue of fraud amongst politicians when he is not in Parliament.
Mangkorn Yontrakul, a former chairman of the Roi Et province administrative body, will take his place in Parliament.
Sereepisuth is a former National Police commander. He is known by the moniker "Hero of Nakae" due to his success in tackling the communist groups in Thailand.