"I do not believe I would receive a fair trial," Ungpakorn told British publication "The Guardian". The 54-year-old political scientist, who holds dual citizenship, had been charged with defaming the monarchy over his book 2006 "A Coup for the Rich", which criticized the coup staged by Gen. Sonthi Boonyaratkalin on that year.

"The Nation" quoted him as saying that the lese majeste charges against him were politically motivated because they were filed more than a year after the book had been published.

Shortly before Ungparkorn left Thailand, he posted a strongly worded letter on the Internet calling for more freedom of expression in Thailand.

"We need to have freedom of expression. Freedom to choose a government that the majority wants without suppression, without threat and fear," part of his manifesto said.

Lese majeste is a criminal offense in Thailand, carrying a 15-year prison sentence.