Capt Thammanat Prompao gestures as he talks to reporters on Thursday about his case in Australia. (Photo by Pattarapong Chatpattarasill)

Deputy Agriculture and Cooperatives Minister Capt Thammanat Prompao -- who is at the centre of a controversy facing the new cabinet line-up -- insisted on Thursday he had been cleared of all criminal charges from his past.

In separate interviews which aired on News 1 channel and at parliament, Capt Thammanat defended himself against criticism over his criminal past in at least two major circumstances, a drug case in Australia and a murder case in Thailand.

He said the drug case in Australia in 1993 was a misunderstanding as he was only an innocent bystander.

The Australian court's decision to acquit him and all other suspects after he was held in prison for eight months while waiting for the court's ruling was proof of his innocence, he said.

He said he was detained by police along with four other people while staying at a close friend's apartment in Sydney.

The friend who owned the apartment had some friends over that day and the arrest was carried out only a few moments after the guests arrived, he added.

Capt Thammanat was later charged on suspicion of being involved in a drug gang but not for dealing himself, he said.

After being acquitted of the charge, he was discharged and required to complete six months of community service.

After being released, he started a business producing tissue paper in New South Wales until he was sent back to Thailand by the Australian government despite him not having any outstanding immigration condition or any suspicion of involvement in criminal activities.

After returning to Thailand, he was arrested and detained in prison for three years in connection with the murder of a gay man, he said.

The Criminal Court acquitted him after finding two other men guilty in the case, he insisted.

He was arrested because he owned the office where the murder took place, he said.

The outcome was final because the prosecutor didn't appeal against the Criminal Court ruling, he said.

Seri Ruam Thai Party leader Pol Gen Sereepisuth Temeeyaves said opposition parties were in talks over the possibility of submitting a censure debate motion against Prime Minister Prayut Chan-o-cha who proposed the appointment of Capt Thammanat as a cabinet minister.

The opposition is also seeking to have the Election Commission held accountable for certifying Capt Thammanat whom Gen Sereepisuth said has ethical problems, he said.

The discussions among the opposition parties on this matter is expected to take about two days.