"The recent spike in lese majeste cases pursued by the police and the courts shows the urgency to amend them," said Frank La Rue, the U.N. special rapporteur on the right to freedom of opinion and expression. He said the laws' vagueness is in contravention of international treaties.
He said section 112 of the Thai penal code states: "Whoever defames, insults or threatens the king, the queen, the heir to the throne or the regent shall be punished with imprisonment of three to 15 years."
He also said Thailand's Computer Crimes Act can impose jail terms of a possible five years for any views on the monarchy posted on the Internet and deemed to threaten national security.
Thais revere royalty and King Bhumibol Adulyadej, 83, is the world's longest-reigning monarch.
The call comes when a U.S. national of Thai origin has pleaded guilty to defaming the royal family stemming from accusation of posting online a translation of a banned biography of the king.
Britain's Daily Mail reported Joe Gordon would face sentencing next month, even though his alleged crimes occurred years ago while living in the United States.