They attacked the 90.50 Mhz radio station, located near a private bus terminal on Mae Sot - Tak road in tambon Mae Pa. The station was set up and operated by Wuthipong Kachathamkul, alias Kotee, a well-known red-shirt leader in Pathum Thani.
Chartchai Ua-angkoonkachorn, the Mae Sot red-shirt leader who is to be the station's director, told police that three or four men arrived on a pick-up truck about 4am. They stopped the vehicle near the bus terminal and opened fire at the radio station.
Security guards at the station returned fire and they exchanged shots for about 10 minutes before he attackers withdrew.
Mr Chartchai believed one of the attackers was shot and wounded.
He said 28 bullet holes were later found on the walls of the station building and a car, but nobody was hurt.
Mr Chartchai said Mr Wuthipong planned to open the station for a trial broadcast on March 28. The official opening of the station was set for April 5. A large number of red-shirt leaders from other provinces were expected to attend, he added.
Mr Wuthipong, who was believed to be the target, was not in the station at the time of the attack.