In the northeastern Thai city of Khon Kaen, Pongpit Onlamai, a prominent anti-junta "red shirt" member, points to a man seated in the corner of the cafe fidgeting with his phone.

"Soldiers are always following me around," Pongpit, a DJ at a red shirt radio station before it was shut down after last May's military coup. "Today, this guy's here."

At one point the man, dressed in civilian clothes, raises his phone, appearing to take a photograph of Pongpit.