
Ploen Thannyapot, 47, Siriporn Sawetsomboon, 36, Nittaya Nenthong, 45, and Samai Passapan, 33, all from the province, were charged with destroying property and physical assault and attempted battery.
The suspects confessed, saying they were trying to attract political attention.
Sombun Khunthongthai, the leader of the red-shirt protest, was booked on the same charges but flatly denied them, saying police ordered him to find a scapegoat for tossing a ping-pong bomb at the motorcade.
Police feared being transferred if he could not find the bomb-thrower but he refused to look for the scapegoat, he said.
"There is evidence incriminating the suspect. Police just have to look at the video clip,'' he said.
Hundreds of red-shirt protesters had gathered at the College of Local Administration on Saturday, as Suthep was about to hold a meeting with local leaders.
After the meeting, as Suthep was leaving the campus in his car, the demonstrators flung eggs, shoes, water bottles and a homemade explosive device, hurting a cameraman for NBT station.
Suthep instructed police to bring those responsible for the violence to justice.