Police plan to prosecute anti-government demonstrators who allegedly damaged police headquarters, splashed paint and fired slingshots at police during Wednesday night's rally at Ratchaprason intersection in downtown Bangkok.
After the protesters dispersed, Pol Col Kissana Phathanacharoen, deputy spokesman, said demonstrators had thrown objects at the headquarters building and splattered paint all over its signboard.
Pathumwan police were compiling evidence and preparing a case for prosecution.
Demonstrators also used slingshots to fire metal bolts and glass marbles at riot police, and splashed oil paint on officers' faces, which caused irritation to their mouths and eyes.
Interrogators were still compiling their list of injured police, Pol Col Kissana said.
The demonstrators had not sought permission for their rally at Ratchaprasong intersection. They had been warned of regulations about rallies, the spokesman said.
Pol Col Krissana said police were trying to prevent violence, and clashes between opposing groups of demonstrators such as occurred near the parliament complex in Dusit district on Tuesday.
Pol Col Siriwat Deepor, a deputy spokesman of police, said on Thursday that anti-government demonstrators on Wednesday also sprayed paint on 13 surveillance cameras, to prevent their actions being observed, and damaged the signboard, fence and lamps at police headquarters.
Police were estimating the damage and Special Branch police had already filed a complaint about the damage at Pathumwan police station.
He said three border patrol policemen were slightly injured by objects thrown from outside the police head office, and a police car from Suwinthawong station had its tyres punctured and was sprayed with paint.
"Demonstrators have their legal right to rally, but they must not damage public properties acquired with the money of nationwide tax payers," he said.
Anti-government demonstrators led by former and present university students rallied again on Wednesday night, this time at Ratchaprasong intersection, which is adjacent to police headquarters.
They are demanding constitutional amendments, the resignation of Prime Minister Prayut Chan-o-cha and reform of the royal institution.
Their street protests started in July and are continuing on scheduled dates. They have begun using rude language to support their demands.
They are often being confronted by rival demonstrators wearing yellow who oppose constitutional amendment and vigorously support the monarchy.
