The National Anti-Corruption Commission (NACC) on Tuesday said it will ask Gen Preecha Chan-o-cha, Prime Minister Prayut Chan-o-cha's younger brother, to acknowledge charges of concealing assets belonging to himself and his wife.
The commissioners voted 9-0 that there were grounds to the allegation against Gen Preecha, also a senator, a source said.
Niwatchai Kasemmongkol, the NACC deputy secretary-general, told Isranews Agency the NACC was in the process of laying charges against the accused.
Gen Preecha would give further statements to the commission before the case is concluded. After that the case will be submitted to the commissioners who will decide whether to forward it to prosecutors.
He was accused of falsely declaring his assets and liabilities while serving with the National Legislative Assembly formed after the National Council for Peace and Order toppled the Pheu Thai-led government in 2014.
The alleged false declaration has to do with Gen Preecha's failure to include his house in Phitsanulok and a bank account belonging to his wife, Pongpuan, in the couple's asset list.
Gen Preecha said he explained everything to the commission in January and February and would let the law run its course.
He insisted that he filed his assets and liabilities properly.
The NACC also found grounds to allegations against three current MPs and one former MP who allegedly let fellow lawmakers use their voting cards in parliament, said a commission source.
In one case, Chalong Thoetwiraphong, a Bhumjaithai MP for Phatthalung; Phumsit Khongmi, a Bhumjaithai MP for Phatthalung; and Natee Ratchakitprakanr, a former Bhumjaithai list MP, were accused of dereliction of duty for allowing other lawmakers to get hold of their MP cards to vote during a House deliberation of the budget bill last year.
In another case, it is alleged that Thanikan Phonphongsarot, a Palang Pracharath Party MP for Bangkok, gave her card to a fellow MP to vote on her behalf.
The six involved could face up to 20 years in prison, a fine of between 20,000 and 200,000 baht, or both.