They also laid a wreath in front of the RTPO, saying the police had not rushed to find the culprits who were responsible for the death of Thirsak Phokaew.
The demonstrators, in a statement read in front of the police office, gave the police until Dec 25 to clear up the case otherwise they would stage a mass protest to call for justice and condemn them.
The protesters, both on Rama 1 road and on the skywalk, blew whistles and shouted continuously in demanding the government's ouster. Some of them reportedly threw rocks and other objects into the police premises.
A number of anti-riot and Special Branch police earlier deployed in front of the national police office were withdrawn to avoid confrontation and reduce tensions.