A leading forensic doctor has asked for autopsy report of a taxi driver who protested the coup by hanging himself from a pedestrian flyover on Wednesday.

Dr Pornthip Rojanasunand together with Charan Ditthapichai, a National Human Rights Commission member and Dr Weng Tohjirakarn, a pro-democracy activist, visited Forensic Institute's deputy chief Dr Lieng Huiprasert.

The group then inspected body of Nuamthong Praiwal, 60, a taxi driver who slammed his taxi into a tank at the Royal Plaza in September. He was found hang himself from a pedestrian flyover over Vipavadi Rangsit Road on Tuesday night in an apparent protest to the coup.

Found with him is a note which said, "I am a taxi driver who has sacrificed himself for democracy." [Click here to read the note]

Dr Pornthip said she was asked by Federation for Democracy to examine the body to make sure that there is no foul play.

"I also consult with Army Commander in Chief Gen Sonthi Bunyaratglin who said that Justice Ministry and Royal Thai police should cooperate to make clear the cause of the death of Nuamthong," she said.

Initial examination showed that Nuamthong died of suffocation, she said, adding blood test is necessary to look for other substances.

She said she could not say whether it is a murder or a suicide.

Earlier, Pol Col Phaisarn Kojasup, commander of Bang Sue police station, said Nuamthong was found hung from a rail of the pedestrian flyover on Vibhavadi-Rangsit Highway in front of Thai Rath newspaper head office.

A passer-by spotted the body and informed police at 20 minutes after midnight.

A handwritten note was found near the body, saying the death was to protest against a spokesman of the Council for National Security for saying he had no ideology in his earlier protest against the coup.

A source from iTV said the man called a reporter of the station before his death, asking the reporter, who had earlier interviewed him, to keep the tape of the interview well because it could be put into a good use soon.

The station played the tape after his death but, the source said, the miltary called the station to stop airing it.

Phaisarn said the surrounding evidences indicated that the man committed suicide.

Nuamthong made headlines on September 30 when he slammed his taxi into a tank at the Royal Plaza at 6 am. He spray painted his purple taxi with the words, "Destroy the country" and "Suicide".

He suffered broken ribs at that time.

Nuamthong's wife, Boonchu Praiwal, 51, said she was proud that her husband sacrificed his life for the country.

"I was very sorry to lose the family head. I didn't expect that he would be so brave. But I am proud of him. I am proud that he sacrificed his life for the country," Boonchu said.

She said Nuamthong left their house at noon Tuesday but she did not ask him where he would go.

Reacting to the tragedy, Prime Minister Surayud Chulanont said he was saddened by the death but doubted there would be any copycat suicide bids.

"We can talk to find ways to solve our problem and explain the reasons" for the coup, he told reporters.

On September 30, Nuamthong spray-painted his purple taxi with the words "Destroy the country" and "Suicide" before slamming his vehicle into a tank at the Royal Plaza in central Bangkok.