Thailand's military government has warned its citizens against online interaction with three prominent critics, saying they could face prosecution.
In an unprecedented move, the Ministry of Digital Economy and Society advised against following, contacting or sharing content from the three men.
Those who did could be in violation of the Computer Crimes Act, it warned.
A rights group said it "showed brazen determination to silence dissent".
The three people are historian Somsak Jeamteerasakul, academic Pavin Chachavanpongpun and journalist Andrew MacGregor Marshall.
All three currently live outside Thailand and are active on social media.
They have spoken about the military government, the monarchy and the use of the Lese Majeste law - strict regulations that block any criticism of the royal institution but which rights groups say are used to stifle dissent.
'Tools to suppress dissent'
An official from the ministry, Somsak Khaosuwan, said the order was to "benefit the people so they can search for the right information... and use their judgement so that it (the order) will not affect them".
But Amnesty International, in a statement, said Thai authorities had "plunged to fresh depths in restricting people's freedoms of expression".
"After imprisoning people for what they say both online and offline, and hounding critics into exile, they want to cut people off from each other altogether," Deputy Director for South East Asia and the Pacific Josef Benedict said.
Thailand has been run by the military since it ousted an elected civilian government in 2014.
Widely-revered King Bhumibol Adulyadej, who had spent decades on the throne, died in October 2016. He has been succeeded by his son, King Maha Vajiralongkorn, who is yet to enjoy the same level of popularity as his father.
In its latest report in March, the UN Human Rights Committee expressed concern about freedom of expression in Thailand. It called on Thailand to stop using criminal defamation laws and provisions such as the Computer Crimes Act as "tools to suppress the expression of critical and dissenting opinions".