BANGKOK - The new United States ambassador to Thailand is under probe for alleged lese majeste over comments that he made at an event in Bangkok last month.

Mr Glyn Davies, who took up his post in September, triggered protests by royalists in the kingdom after he raised concern about Thailand's lese majeste law during a talk at the Foreign Correspondents' Club of Thailand (FCCT).

Thai police on Wednesday (Dec 9) confirmed that an official investigation was taking place.

"He has not been charged yet by the Thai authority since we are undergoing an investigation into the case," deputy national police spokesman Kissana Phathanacharoen told The Straits Times.

Club president Jonathan Head said it had been asked by the Thai police to assist with the probe. "The FCCT is cooperating with the police," he said in a statement.

The US Embassy did not respond to The Straits Times' queries by press time.

Under Thailand's lese majeste law, those found to have defamed or insulted the monarchy can be jailed for up to 15 years for each offence.

Anyone can make a complaint about lese majeste, and the police are obliged to investigate every case.

The number of prosecutions and the severity of the sentences have spiked since the military seized power through a coup last year. Military courts now hear lese majeste cases.

In August, a man was jailed for 30 years for insulting the monarchy on Facebook.

Mr Davies raised the issue during his talk on Nov 25 at the FCCT.

"We're also concerned by the lengthy and unprecedented prison sentences handed down by Thai military courts against civilians for violating the lese majeste law," he said.

"We believe no one should be jailed for peacefully expressing their views and we strongly support the ability of individuals and independent organisations to research and to report on important issues without fear of retaliation."

On Dec 3, Mr Sonthiya Sawasdee, who reportedly belongs to a royalist group called Federation to Monitor The Thai State, filed a complaint against Mr Davies at the Crime Suppression Division.

tanhy@sph.com.sg