Facebook Thailand could face legal action next week after Thai authorities warned Facebook to take down content deemed threatening to national security or violating strict "lese majeste" laws, the telecoms regulator said on Friday.

Thailand's military government has ramped up online censorship, particularly perceived insults to monarchy, since seizing power in a 2014 coup.

The National Broadcasting and Telecommunications Commission said Facebook had failed to remove 131 of 309 web addresses on its platform which were threatened security or violated the lese majeste law, which makes it a crime to defame, insult or threaten the king, queen, heir to the throne or regent.

They formed part of some 6,900 web addresses which Thai courts have ordered to be removed or shut down since 2015.

Takorn Tantasith, secretary-general of the commission, said he had given Facebook until Tuesday to remove the 131 addresses.

"If Facebook still shows content declared illegal by court orders in Thailand, action must be taken against Facebook Thailand," Takorn told Reuters.

"They could argue that they are not involved (in removing content), but Facebook Thailand is still operating here."

He said the Ministry of Digital Economy would file a complaint with police next week to press charges against Facebook Thailand under the Computer Crime Act and commerce ministry regulations.

He also said obtaining a search warrant for Facebook Thailand would be a possible step.

Facebook has not responded to Reuters' request for comment about the threat of legal action against Facebook Thailand.

Facebook Thailand focuses on marketing and business developments in Southeast Asia's second-biggest economy.

Facebook has said its general guideline when it receives requests from governments to remove content is to first determine whether the content violates local laws before it proceeds to restrict access in the relevant country.

Facebook said it blocked 50 pieces of content which were found to have violated the lese majeste law in 2016, following government requests.

Thailand's telecoms regulator has taken a tough stance against perceived criticism of the monarchy since Thailand's revered King Bhumibol Adulyadej died in October.

It has pressured internet service providers to monitor content and block anything inappropriate.

Thailand considers the monarchy to be one of the guiding pillars of Thai society and above criticism or comment.