BANGKOK (AFP) - Thailand declared British former glam rocker Gary Glitter "persona non grata" Wednesday and threatened to deport him back to Vietnam, where he has just finished prison time for child sex offences.

The 64-year-old was due to have boarded an overnight flight to London from Bangkok but was still wandering the airport transit lounge more than 16 hours after flying in from Vietnam.

He initially complained of chest pains, refusing to board the Thai Airways plane to the British capital, but it was unclear what would happen next.

A doctor examined him in the transit lounge and said Glitter was suffering from a minor inflammation in his chest, declaring him fit to travel, a medical official at the airport told AFP.

Thailand's immigration chief said Glitter refused to board the next flight to London but had been declared persona non grata and would not be allowed to enter Thailand.

"We will have to repatriate him back to Vietnam, because he is on our watch list as persona non grata. Thai immigration cannot let him enter," Lieutenant General Chatchawal Suksomjit told AFP.

The terms of Glitter's sentence called for his deportation upon his release from jail, and it appeared unlikely Vietnam would allow him to return.

"He could be returned to his homeland since we do not want him here," said Thailand's Interpol commander, Colonel Apichat Suriboonya.

Glitter arrived here from Vietnam late Tuesday after spending two years and nine months in jail for committing obscene acts with two girls aged 11 and 12 in the southern resort town of Vung Tau in 2005.

The British embassy in Bangkok said they had offered him consular help but that his fate was up to Thailand.

"It's a matter for the Thai authorities," the embassy said in a statement.

Britain has not announced any outstanding charges against the singer once famed for his flamboyant bouffant wigs and silver jumpsuits, but British Home SecretaryJacqui Smith said he should not be allowed to leave if he returns.

"We need to control him, and he will be, once he returns to this country," Smith told talkSPORT radio.

She said Glitter -- real name Paul Francis Gadd -- would have to sign a sex offenders' register and notify authorities if he wants to travel abroad.

"It certainly would be my view that with the sort of record that he's got, he shouldn't be travelling anywhere in the world," she added.

Glitter had several hits in the 1970s including "I'm The Leader Of The Gang (I Am!)" and "Do You Wanna Touch Me?"

The anthemic 1972 hit "Rock and Roll" is still often chanted in British and US sports stadiums.

He was arrested in Britain in 1997 after he took his computer to a repair shop, where hardcore child pornographic material was found on its hard drive. He was sentenced in 1999 to four months in prison, of which he served two.

Keen to avoid the media, Glitter reportedly moved first to Cuba and then Cambodia, where he was expelled in 2002, allegedly for trawling for underage sex.

Having settled in Vietnam, where a British newspaper reported he was living with an underage girl, he was arrested at Ho Chi Minh City airport in November 2005 while trying to leave for Thailand.

In March 2006 he was sentenced to three years in prison, the minimum term under Vietnamese law, which was later cut by three months.

The singer maintained his innocence, blamed a media conspiracy and claimed he was teaching the girls English and allowed them to stay overnight because they were scared of ghosts.

Child protection workers called for his deportation back to Britain.

"We don't feel it's appropriate he spends his time hopping from one country to the next one while countries decide what to do with him," said Mark Capaldi, deputy director of Ecpat International, a child protection charity.