BANGKOK, June 5 (CGTN) -- Thailand's former prime minister, former Democrat Party leader Abhisit Vejjajiva on Wednesday announced his resignation as MP, before voting for the new prime minister of Thailand.

At the TOT Public Company Limited's head office in northern Bangkok, which is being used as a makeshift parliament, Abhisit said he had to keep his word.

Abhisit apologized to all the people who had voted for his party and candidates in the nationwide election for the failure to put his pledged standpoint to work.

He said he tried his best but the Democrat Party decided on late Tuesday to join the coalition led by the pro-government Palang Pracharath Party.

A joint House of Representatives and Senate meeting is going on on Wednesday during which 500 lower house representatives and 250 senators would elect the new prime minister.