Incumbent Bangkok governor Aswin Kwanmuang said he will tender his resignation on Thursday so that he can run in the city's gubernatorial race, expected in May.
His resignation letter will be submitted to Interior Minister Anupong Paojinda before the Election Commission (EC) announces the schedule of local elections in Bangkok and Pattaya City on Friday, he said.
Pol Gen Aswin will meet the media on Thursday to address all questions about his decision.
After he steps down, the city clerk will run the Bangkok Metropolitan Administration (BMA) on a caretaker basis until the new governor is elected and takes office.
Labour Minister Suchart Chomklin avoided answering questions about whether the Palang Pracharath Party (PPRP) would support Pol Gen Aswin to run under the ruling party's banner.
He merely said the party would hold a plenary session in Nakhon Ratchasima to discuss the matter on April 3.
When asked to confirm if the PPRP would name its candidate for the Bangkok governor election, he was non-committal, explaining he could not speak for other party executives.
He also declined to comment on whether the PPRP would support Pol Gen Aswin in the coming election in any capacity.
Deputy Prime Minister Prawit Wongsuwon, in his capacity as PPRP leader, also refused to comment when pressed on whether the party would name its candidate for the Bangkok governor election on April 3.
Pol Gen Aswin has said he will run as an independent.
While seemingly reluctant to be pinned down on who the PPRP would back for city governor, Mr Suchart said the party has decided to field candidates in the election of Bangkok councillors.
He said he saw no need for the party to be represented by both the Bangkok governor and councillors simultaneously. The latter could suffice, he said.
Mr Suchart said he believes Bangkok councillors are the more important of the two as they are closer to the city's residents.