A police officer at Ladprao Police Station told the Thai Human Rights Lawyers (THRL) group that the activist had been detained according to an arrest warrant, adding that he had been taken to the 11th Military Circle, the THRL tweeted on Tuesday.

The group had not been able to contact Ekachai as of press time.

The pro-democracy group Resistant Citizens was scheduled to stage a symbolic demonstration at Victory Monument and march to the 11th Military Circle unless Ekachai was released.

A security agency source said Ekachai had been invited for “a talk to create some mutual understanding” at the military circle as the activist attempted to submit a complaint calling for an investigation regarding the missing plaque.

The source said officers were afraid his actions could create confusion in the public.

The talk would take time and Ekachai would be released if a “mutual understanding” was reached, the source said.

Ekachai has been previously convicted of lese majeste and works on behalf of political prisoners at the newly established association For Friends.