The former US Air Force non-commissioned officer pleaded guilty to a murder charge filed by local police in California for the murder of his pregnant wife Sopha in the state in 1994, police said.

The Thai-American has had a Bt1-million bounty on his head since a wanted list was made public earlier this month by Thai and US authorities.

Police initially located Saner on Wednesday with the help of a tip-off that a man with an identity resembling a police sketch was selling charcoal at Khoke Matoom market.

After a two-day stakeout, police approached the subject and brought him to a local police station for further questioning.

Saner's identity was later verified by various documents issued by both Thai and US authorities, including Thai and US passports and a bank passbook.

Speaking at a press conference in Bangkok, deputy police chief General Issaraphan Sanitwong na Ayutthaya said Saner had signed an agreement to have himself extradited to the US for prosecution.

The Bt1-million bounty will then be given to the Thai police by US authorities, but the officer did not say how much the informer who provided the crucial tip-off would receive.

Saner said he had contemplated suicide several times, and felt as if he had died the day after

he killed his wife. "I have been

living in misery all along. I have been living on given time. No happiness or anything at all," he added.

He said he had never withdrawn any of the Bt3 million he earned through serving in the USAF, for fear he could be traced.

Saner said he had killed Sopha out of rage after learning that she was eight months pregnant, despite nearly a year without sex together. He said he had struck her on the back of her head with a hammer while she was watching television, while their two children were out. He later put her body in a container and dumped it at a location 50 to 60 kilometres from his home.

He claimed Sopha was also a gambling addict and had wasted a lot of money on card games.

The man said he had not seen his children since the murder, and learned that his son had frequently come to Thailand in search of him.

"I will not meet him even if he is still here now, as I can do nothing to help him," he said.

Saner added that he had often come to Thailand, and had then moved around. Most of his jobs here had been painting advertising banners.