An Australian writer accused of defaming Thailand's royal family in his 2005 novel was arrested at Bangkok's international airport as he was about to board a flight home, a press freedom organization said Friday.

Harry Nicolaides apparently did not know that an arrest warrant had been issued against him in March in connection with his novel, "Verisimilitude," the Paris-based group Reporters Without Borders said.

Nicolaides, a 41-year-old Melbourne resident who lived in Thailand from 2003 to 2005, taught in the northern Thai city of Chiang Rai. Nicolaides has described his novel as a commentary on political and social life of contemporary Thailand. It is not clear where it has been published.

He was arrested Aug. 31 on a warrant accusing him of defaming Thailand's royal family, according to a statement Friday from Reporters Without Borders.

"Nicolaides is aware of the limits on criticism in Thailand. His novel never intended to threaten or defame the royal family," the group said. "We call on the authorities to drop the charges against him and to release him."

Thailand is a constitutional monarchy, but has severe lese majeste laws, mandating a jail term of three to 15 years for "whoever defames, insults or threatens the king, the queen, the heir to the throne or the Regent."

Actual prosecutions are relatively rare — usually a handful each year — not surprising in a country where the 80-year-old king is almost universally revered as a selfless and hardworking benefactor of the people.

The severity of the laws was highlighted around the world last year when a Swiss man, apparently acting in a drunken frenzy, was found guilty and given a 10-year prison sentence for defacing images of the revered monarch. He was pardoned by the king after serving about a month behind bars.

Other cases involve ordinary citizens spreading political rumors or prurient gossip about the royal family.