Speaking at a press conference to update the public on the protest situation, Capo spokesman Pol Maj Gen Piya Uthayo said the authorities are concerned that three rally sites occupied by demonstrators with the People's Democratic Reform Committee are vulnerable to violent confrontation between protesters and people who have been affected by shutdown road blockades.
The three areas at risk are Chaeng Wattana Road, Lat Phrao intersection and Victory Monument.
Chaeng Wattana Road and Lat Phrao are close to Don Muang, once a Pheu Thai, red-shirt stronghold.
Capo is meanwhile investigating three violent incidents that occurred in the early hours of Monday morning, just hours before the shutdown rallies kicked off.
Pol Maj Gen Piya said the first incident, which took place shortly after midnight on Soi Chaeng Wattana 14, involved a shooting attack that left 36-year-old PDRC security guard Samran Chanthong injured.
Two teenagers on a motorcycle argued with Mr Samran after he refused their request to pass through a road barricade. A fist-fight ensued and he was shot in the neck.
At 1.20 am, police were called to the home of PDRC leader Rachen Trakoonwiang in Nonthaburi province, after a hand grenade was hung on the fence of his home by an unidentified assailant.
One hour later, a gunman fired 13 shots at Democrat Party headquarters on Samsen Road. The bullets hit the front of the party's coffee house and no one was injured.
Security camera footage showed a man sitting in the back seat of a grey Toyota Vios opening fire on the building from an unknown type of gun.
“The incidents last night are a signal of possible escalating violence, therefore we appeal to the public to help monitor [incidents] and alert police. The police will try to ensure peace and order are maintained during the protest rally,” Pol Maj Gen Piya said.
National police chief Adult Sangsingkaew had instructed police to ensure all culprits in Monday’s attacks are punished, Pol Maj Gen Piya said.
Capo believes the shutdown rallies will last for another four or five days, he said.
Police meanwhile arrested eight PDRC security guards from an apartment room in Ramkhamhaeng Soi 53 for possessing kratom leaves and cannabis, the Capo spokesman added.