Tarit Pengdith, former director-general of the Department of Special Investigation, was on Friday given a suspended three-month jail sentence and fined 5,000 baht for concealment of assets worth tens of millions of baht while in office.
The Supreme Court's Criminal Division for Holders of Political Positions also prohibited him from holding a political appointment for five years.
The National Anti-Corruption Commission (NACC) earlier accused Tarit, 59, of trying to hide assets by failing to include several bank accounts and valuable properties in his declaration of assets and liabilities while serving as DSI director-general.
The court found him guilty of not reporting about 5 million baht in four bank accounts, about 6 million baht invested in two companies, buildings on two blocks of land totalling about two rai in Pak Chong district of Nakhon Ratchasima worth 20 million baht, about 6 million baht in bank accounts held by his wife and more money in bank accounts in her nephew's name.
Initially, the Supreme Court sentenced Tarit to six months in jail and a fine of 10,000 baht. It commuted the punishment to a three-month term and a fine of 5,000 baht because he confessed. It suspended the jail term for two years because he had not previously been sentenced to prison.
The ban on holding a political position is effective from April 3 last year, when he was sacked from the position of adviser to the Prime Minister's Office.
The NACC filed the lawsuit against Tarit on Aug 10 last year, accusing him of violating Section 119 of the anti-corruption law by deliberately falsifying his assets and liabilities declaration.
The graft probe against him was launched after the May 2014 coup amid allegations that one of the ex-DSI chief's properties encroached on Khao Yai National Park in Nakhon Ratchasima.
The probe found that the house was held in the name of Tarit's wife, Wassamon, and had not been declared to the NACC as required by law.
According to the NACC's findings, Mr Tarit amassed unexplained wealth of 346.65 million baht while at the DSI.
He was appointed deputy director of the agency in 2002 and in 2009 was promoted to director general, a position he held until being dismissed in 2014.