BANGKOK - A Thai pro-democracy activist has been arrested and charged with computer crime after he posted about the end of monarchy on Facebook.

Kan Pongprapap, 25, made no mention of the Thai monarchy when he described how royal rule ended in many countries but posted a screenshot of a tweet made under the account @pnsrmk that was about Thai royalty.

The tweet referred to the frustration of Thais with roads being closed whenever a royal entourage passes by, saying that it adds to the traffic congestion in the capital. The hashtag #royalentourage was trending on Twitter a week ago.

Police said on Tuesday (Oct 8) that Kan was arrested at home in Bangkok late on Monday. He now faces up to five years in prison as well as a fine of up to 100,000 baht (S$4,530) if found guilty of national security-related computer crime.

Both the Facebook post and the tweet have since been deleted. Kan's Facebook account and the @pnsrmk Twitter account have also become unavailable.

Users have been warned that they face the same penalties for sharing the posts.

A statement from the Technology Crime Suppression Division (TCSD) only referred to Kan's post as "inappropriate", while Thai media said the post was about "foreign histories".

"There were around 100 comments and 50 shares of the post, which can agitate the public," said the TCSD.

Thailand's draconian lese majeste law prohibits insults and criticism against the king, queen, heir apparent and regent, with perpetrators facing up to 15 years in prison if found guilty of the offence.

But Thais have become more vocal about their dissatisfaction with the monarchy on Twitter, largely because they do so under fake names and also because Thai authorities primarily monitor Facebook.

Monday's arrest is part of an intensifying crackdown on fake news and online content criticising the government and the monarchy. An anti-fake news centre, manned by staff from the digital economy and society ministry and volunteers, is expected to open by Nov 1.

Kan was part of a movement calling for an election in Thailand as the previous military regime, which came into power in 2014, kept postponing the date for polls until March this year.