Thai activists on Monday demanded the release of a man arrested for sharing an infographic on Facebook detailing alleged graft in an army-built park, saying plainclothes security officers had taken him by force.

Since taking power in a military coup in May 2014, Thailand's ruling junta has issued directives that have largely stifled dissent, including barring political discussions and debate.

On Sunday, a 25-year-old student, Thanet Anantawong, was taken from a hospital while he awaited an operation, said prominent anti-junta activist, Siriwat Serithiwat.