A Thai-born US citizen jailed for insulting Thailand's king has received a royal pardon, officials said Wednesday, a move welcomed by Washington that had issued a rare rebuke to Bangkok over the case.

Joe Wichai Commart Gordon, a car salesman from Colorado, was sentenced to two-and-a-half years imprisonment in December under Thailand's lese majeste laws, which rights campaigners say are used to stifle freedom of expression.

The 55-year-old was arrested in May 2011 while on a visit to Thailand, after he had posted material online from his own Thai translation of a banned English-language biography of King Bhumibol Adulyadej.

Gordon "was granted a royal pardon yesterday," a senior Corrections Department official said on Wednesday. The Bangkok Remand Prison said he left the jail late Tuesday.

Gordon was taken to the US embassy on release, according to his lawyer Anon Numpa.

Hours before he was freed, Gordon said he had heard that he could be allowed out but could not quite believe it.

His conviction put the international spotlight on Thailand's increasingly controversial lese majeste prosecutions, drawing protests from the US, which had said Gordon was exercising his right to free expression.

Under the legislation, anyone convicted of insulting the Thai king, queen, heir or regent faces up to 15 years in prison on each count.

AFP