TJA made the demand after a video clip uploaded to YouTube by Matichon TV showed a plainclothes policeman arresting a woman protester during an anti-coup rally near Asoke BTS station on Sunday.
The officer was seen wearing what appeared to be a press badge and a green armband issued by TJA around his neck.
Witnesses and foreign journalists confirmed the policeman was wearing a TJA armband, said TJA spokesman Manop Thip-osod.
The TJA was “deeply concerned” about the incident because such action affected work, safety and credibility of reporters and photographers.
It demanded acting national police chief Pol Gen Watcharapol Prasarnrajkit and deputy police chief Pol Gen Somyos Poompanmuang, who oversees political rallies, review the use of the media armband by undercover police.
Mr Manop said each armband has the logo of the TJA and the Thai Broadcast Journalists Association as well as information about the reporter and their media outlet. This ensured that members of the press have been working openly at political rallies over the years.
“Police have several ways of disguising themselves to make arrests or gather intelligence, but [doing this] has a big impact on media people generally.” Mr Manop said.
“If they don’t review it, the association will consider taking legal action against those people who are not journalists and misuse these armbands, without exception.”
New armbands would be developed and issued that were difficult to counterfeit and that identify the wearers more clearly.
Mr Manop urged all members of the media to immediately inform their bosses if they lose their armbands and not give them to news sources in security agencies, or to other individuals.