Thai police arrested three people on the streets of the capital on Sunday after they held a small gathering to "exchange views" with the country's military junta.
Thailand's military has severely restricted public gatherings since seizing power in a coup last May. Taking a hard line on dissent, it has detained more than 300 people, including activists, journalists and politicians.
The leader of a group of four people, Akkarakit Noonchan, was dragged away by plainclothes officers shortly after the beginning of the event at Bangkok's downtown Victory Monument, according to a Reuters witness.
Akkarakit told reporters that the group, calling itself Serichon Thailand 58, did not intend the gathering to be a protest.
They had earlier displayed t-shirts depicting a bird with its beak and claws bound, as dozens of uniformed police stood by.
Akkarakit, 47, and two others were held for several hours by the army for "attitude adjustment" before they were released to police and charged with disturbing the peace, Lieut. Col. Wichai Daengpradab told Reuters.