Kitti Pantapak, a Prachatai reporter, 24, was arrested in front of MBK Centre while reporting live on Facebook about the police crackdown in Bangkok on the night of 16 October.
He was later released at 2.00 on 17 October after paying a 300 baht fine for defying an official order.
When arrested, he was wearing a press armband from the Thai Journalists Association, which identifies the media and distinguishes them from protesters.
Footage from Kitti on Facebook Live shows that he was asking a police officer about where he would be able to stay and cover the news. Police then approached him and grabbed his camera.
Kitti then says "I have been detained already" and the live video was cut. His camera and mobile phone were also taken from him.
Around 22.00, Prachatai was able to locate him sitting in a police detention truck along with other 2 protesters. He was taken to nearby Pathumwan Police Station and then to Border Patrol Police Region 1 headquarters in Khlong Luang, Pathum Thani, where other protesters were also detained.
Caption: Kitti was handcuffed on a detention truck.
When Prachatai staff arrived, their request to visit him was rejected.
The Thai Journalists Association tweeted at 23.00 that 6 journalist organizations had been notified about the arrest and had been working with related parties.
Update: Kitti's released
Kitti was later released at 2.00 on 17 October after paying a fine of 300 baht for defying an official order under Section 368 of the Criminal Code.
The police had returned his mobile phone and camera to Prachatai staff before Kitti's release, lifting a concern that he might be charged under the 2017 Computer Crime Act.
The arrest of Kitti was in the context of the Emergency Decree which prohibits publishing or broadcasting information which threatens stability. The law was not enforced against reporters covering yesterday's protest (15 Oct).