The Facebook group, Royalist Marketplace, was blocked late on Monday after the social media giant bowed to pressure from the Thai government.
The monarchy is considered sacrosanct in Thailand and any criticism is normally kept private.
Facebook said that while people in Thailand can no longer access the page, it is still available in other places, adding that the company plans to “legally challenge” the government’s request.
“After careful review, Facebook has determined that we are compelled to restrict access to content which the Thai government has deemed to be illegal,” the company said in a statement.
Pavin Chachavalpongpun, a 49-year-old academic who created the group in April, bemoaned the decision, and quickly set up a similar Facebook group that already has hundreds of thousands of members.
“I’m furious, you know, because this is something that I am passionate about. I am passionate because I just want to see Thailand becoming more and more democratic,” Mr Pavin, who lives in exile in Japan, said in an online interview.
Mr Pavin was not in Thailand when the country’s current Prime Minister, Prayuth Chan-ocha, orchestrated a military coup in 2014, when he was the army chief. Following the coup, the ruling junta summoned critics of the government and monarchy, including Mr Pavin, who decided to remain abroad.
Mr Pavin, who is an associate professor at Kyoto University’s Centre for Southeast Asian Studies, said Royalist Marketplace achieved 1 million members just a few days ago. He criticised Facebook for the move.
“By accepting the requests, whether you like it or not, you become a part of that, you become a part of the support that you gave to the authoritarian regime in Thailand,” he said.
Facebook acknowledged the seriousness of blocking the page, saying that such government requests “have a chilling effect on people’s ability to express themselves”.
“We work to protect and defend the rights of all internet users and are preparing to legally challenge this request,” the company said in its statement.
Mr Prayuth said at a news briefing following a cabinet meeting on Tuesday that the government asked Facebook to block the page because it violates Thai law. He said the government would stand firm on its stance if a legal challenge to the request is made.
Mr Pavin said that after the Facebook group was blocked, he immediately created another one that is essentially the same, called Royalist Marketplace-Talad Luang. Talad Luang is Thai for Royalist Marketplace.
The new group has already attracted more than half a million members, with many from the original one migrating over.
