BANGKOK (REUTERS) - Thailand's digital minister vowed not to relent on Wednesday (Aug 26) in a crackdown on social media content deemed illegal.

It was also unlikely that Facebook would follow through on plans to challenge an order to block access to a group critical of the Thai monarchy, the minister said.

The "Royalist Marketplace" group, which had more than one million members, was blocked within Thailand late on Monday after the Digital Ministry threatened legal action against Facebook under the country's Computer Crime Act.

Facebook said it was compelled to comply and would mount a legal challenge in court.

The tension comes amid near daily youth-led protests against the government of a former junta chief, during which some demonstrators have made unprecedented calls for reforms of the monarchy, which is illegal to insult in Thailand.

Meanwhile, a new group with a similar name created by self-exiled academic Pavin Chachavalpongpun, who is also a prominent critic of the monarchy, has amassed more than 700,000 members in just two days.

"If they start a new group or do anything illegal again, we'll need to act again. We'll keep doing this no matter how many times it takes," Digital Minister Puttipong Punnakanta said.

He said he was encouraged by Facebook's compliance with a deadline to act on court orders, which were attached to government request to block content locally. He warned Facebook's Thailand office of possible cybercrime charges if the orders were not observed.

"This time Facebook complied in blocking everything we flagged, which is why I don't think Facebook will pursue legal action," Minister Puttipong said.

"We're not bullies. We use Thai laws to protect Thai cyber sovereignty."

Facebook caving to Thai government pressure set a dangerous precedent for freedom of expression online, said Ms Rasha Abdul-Rahim of rights group Amnesty International.

"It's welcome that Facebook is now planning legal action to challenge the government's censorship demands, but the harm has already been done," she said.

"The company should not have given in to the demands in the first place."