Until six days ago when the men in uniform led him away at Bangkok airport, Harry Nicolaides was just one more flamboyant expatriate in Thailand. He visited first from Australia five years ago, and made his living as an English teacher with a bit of writing on the side.

He wrote seedy columns about his escapades with Thai bar girls and serious articles about child pornography. He described himself as “an individual who achieved brilliance with raw talent and tenacity”. He liked to wear Panama hats and cream suits.

Last Sunday, as he was about to board a flight home to Melbourne, his career came to a crashing end.

Since then he has been locked in a cell - ill, scared and suicidal, and facing a 15-year sentence on one of the gravest charges in the Thai criminal code. Mr Nicolaides, 41, is not a drug smuggler or gunrunner, like plenty of the other foreign prisoners here. The trouble in which he finds himself is over nothing more vicious than an obscure and forgotten book.

Mr Nicolaides is the latest person to be charged with lèse-majesté, the crime of defaming the monarchy. In 2005 he published a novel entitled Verisimilitude, which contains references to rumours about the “romantic entanglements and intrigues” of the family of the Thai king, Bhumibol Adulyadej, and particularly his son, Crown Prince Maha Vajiralongkorn. The contentious material amounts to 103 words that could change Mr Nicolaides' life.

In an interview with The Times at the Bangkok Remand Prison yesterday, he said that he has suffered from a seizure and fever and has been unable to sleep in a cell that he shares with 90 Thai detainees, some of whom are hostile because of the charge against him.

“I've been getting icy stares from men covered in tattoos,” he said. “On the first night I would have committed suicide if I'd had the means ... I want to immediately apologise to the Royal Family for my reckless choice of words. I want to write a letter of apology, with the greatest humility.”

Mr Nicolaides says that before publication he wrote to Thailand's Bureau of the Royal Household, asking for their reaction to the contentious paragraph, and received no reply. He has raised 500,000 baht (£8,200) bail, but this was denied. It is unclear why he has been arrested this week after coming and going over the past seven months. But there seems to have been a general increase in lèse-majesté prosecutions over the past few years.

Within Thailand the law has made any discussion of the role and future of the monarchy impossibly dangerous. There seems to be no limit on what can qualify as insulting the monarchy. Jonathan Head, the BBC's Bangkok correspondent, is under investigation for lèse-majesté. Among the complaints against him is that a photograph of King Bhumibol appeared below that of a Thai politician on a page on the BBC website - rather than at the top.

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