A fact-finding panel has been ordered to be formed to look into a bribery case allegedly involving a former mayor of a municipality in Uthai Thani -- a son son-in-law of Deputy Interior Minister Chada Thaised -- and a number of local officials.
Thap Than district chief Siriwan Kokasetsap said a probe into the matter is expected to wrap up within 60 days.
Weerachart Rasamee, 45, the son-in-law, resigned from his post as mayor of Talukdoo municipality in Thap Than district on Tuesday night after he was released on bail.
He had been arrested on Tuesday morning along with four others for allegedly demanding a 600,000-baht bribe from a tap water contractor.
While Mr Weerachart and the others are facing investigation, a new acting mayor would have to be appointed to ensure day-to-day work continued running, said Ms Siriwan.
Despite his resignation, the investigation launched into his alleged misconduct is still valid and could continue until the end, said Uthai Thani governor Thiraphat Khatchamat.
In his resignation letter, Mr Weerachart denied any wrongdoing, saying he had to resign for political reasons, not as a way of admitting to the alleged crime.
Mr Chada said previously it was he who told the son-in-law to resign and pave the way for the investigation to be conducted into his alleged misconduct.
The case has attracted public attention because Mr Weerachart is a son-in-law of Mr Chada, who is leading the government's attempt to suppress mafia-like influential people, some of whom are believed to be local leaders involved in unlawful businesses and activities.
Asked if Mr Weerachart should be included on a list of mafia-like influential figures, Mr Thiraphat said he had never received any complaint about Mr Weerachart acting as such before.
The province had never heard about Mr Weerachart's alleged misconduct until he was arrested, said the governor.