The Thai Police on Thursday launched an investigation over remarks made by US Ambassador Glyn Davies last month to determine whether the kingdom's lese majeste law was violated.

Thailand's lese majeste laws are among the strictest in the world. It is a crime of violating majesty, an offence against the dignity of a reigning sovereign or against the state.

Since the military coup in 2014, the military junta has brought up 53 lese majeste cases, including 40 for online comments and posts.

In a speech delivered at the Foreign Correspondents' Club of Thailand on November 25, Davies expressed concerns over "the lengthy and unprecedented" prison sentences handed down by Thai military courts against civilians for violating the lese majeste law, Xinhua news agency reported.

Days later, a number of protesters gathered at the US embassy in Bangkok to protest against Davies' remarks regarding the law.

In a statement issued on Wednesday, the FCCT said it has been asked by the Thai Police to assist them in an official investigation into Davies' comments, and "is cooperating with the police".

Earlier, US State Department spokesman John Kirby reportedly said the US government has the utmost respect for the Thai monarchy and Ambassador Davies reiterated long-standing US policy on the issue of freedom of expression.