An academic has fled to Oxford following accusations he insulted the King of Thailand.

Giles Ji Ungpakorn, who is half Thai and half British, claimed he was forced to flee the country of his birth after he was charged with eight counts of lèse majesté — literally translated as insulting the king.

Mr Ungpakorn, 55, said he faced up to 15 years in jail for the allegations he made about King Bumibol in his book A Coup for the Rich.

The associate professor at a Bangkok university, who worked as a lab technician for Oxford University for 12 years in the 1980s and 1990s, said his wife had also received death threats before the couple returned to East Oxford, where they hadbeen staying, on Friday.

Mr Ungpakorn said: “I was extremely worried. In the past people have been bumped off, but my real concern was having to go to prison. The conditions in Thai prisons are pretty appalling.”

Mr Ungpakorn wrote A Coup for the Rich in 2007, shortly after the 2006 military coup. In the book he asked whether the king was manipulated into supporting the coup.

He paid for 1,000 copies to be published, but when he asked his employers, Chulalongkorn University, to sell the book he was refused and a copy was handed to the authorities.

After spending Christmas in Oxford with his 10-year-old son, who attends school here, the father-of-three returned home to Bangkok last month to find a police summons waiting for him.

He went to a local police station, where he was charged and given 20 days to respond before it was decided whether to prosecute him.

Mr Ungpakorn and his wife Numnual headed back to England before the 20 days were up as he said he thought he would be refused bail if the authorities decided to prosecute.

He said: “I was very worried that I would be detained at the airport. My wife thought someone might try and kill me because she received death threats on the phone. She hid it from me but told me later on.

“It was stressful for me and stressful for my wife. My friends and family in Britain were extremely worried as well.”

Mr Ungpakorn, who is currently living in Oxford with family friends, said he would not be able to return to Thailand until there was a regime change.

He said: “I have had to give up my job, my home and everything else. I am calling for a republic in Thailand, as it looks like the monarchy is an impediment to democracy.”

A spokesman for the Thai Embassy in London declined to comment.