The military could be called in to help quell violence at rallies if the situation gets out of hand, while police will stick to using tear gas and rubber bullets if needed, the Metropolitan Police Bureau said.
The police will keep standing guard and avoid clashing with protesters unless they attempt to break into prohibited areas, said Metropolitan Police Bureau commissioner, Pol Lt Gen Pakapong Pongpetra, prior to Wednesday's car mob rally.
"And in the event violence escalates and appears to get out of control, the peace-keeping operation plan will be adjusted by allowing soldiers to fortify the police's defence against violence,'' he said.
The police request for soldiers to help support its operation to maintain law and order at rallies was also discussed at a meeting of the armed forces, which was chaired by defence forces chief Gen Chalermpol Srisawasdi, said a source.
It was, however, agreed that the military are not responsible for dispersing demonstrators, while they are actually responsible for ensuring security at military areas and the palaces, said the source.
He said the police can submit a letter via the Ministry of Defence.
Police fired tear gas and rubber bullets to disperse another anti-government protest in Bangkok on Wednesday.
The demonstration, organised by the Tha Lu Fah group, started at 3pm at Victory Monument.
Hundreds of protesters threw paint at a line of riot police who confronted them as they tried to march to the residence of Prime Minister Prayut Chan-o-cha at the 1st Infantry Regiment on Vibhavadi Rangsit Road.
Police responded with tear gas and rubber bullets to disperse them, and the rally was called off after about an hour.
"Police are not our enemies. Our true enemy is the government," one protester told the rally.
Police blocked the route to the prime minister's house with shipping containers and razor wire.
Tha Lu Fah posted a message on its social media platforms after the clash at the monument, saying young protesters had thrown firecrackers at police as they moved in and started making arrests.
It was Bangkok's second anti-government rally in two days.
In a summary of Tuesday's rally led by the United Front of Thammasat and Demonstration group, Pol Lt Gen Pakapong said 48 suspects, 45 men and three women, have been detained for breaking the law while 122 cars and motorcycles have been seized for inspection.
He said 15 of the 48 suspects were minors.
Nine police officers have been injured during clashes with the protesters, he said, adding that eight officers were injured mostly by ping-pong bombs while the other officer was shot in the leg.
The protesters began breaking the law around 5pm when they started launching ping-pong bombs and giant firecrackers towards police who were standing and forming a human shield to prevent the protesters from advancing, he said.
Around 7pm the violence intensified when the protesters set fire to a small police station in the Victory Monument area, he said.
Pol Maj Gen Piya Tawichai, deputy commissioner and spokesman for the MPB, dismissed rumours on social media that a vocational student was killed during Tuesday's rally.
An investigation into the claim found the student died in a road accident as he rammed his motorcycle into the back of a rubbish truck on the foot of Phra Pok Klao Bridge, he said.
A video clip circulated widely on social media and claimed to have been captured during Tuesday's rally was also found to be fake, he said.
Shown was a number of riot-control police officers smashing a car.
However, it was later found to be footage taken during a 2013 political gathering, he said.
These are examples of violations of the Computer Crime Act, he said, which may lead to a penalty of up to five years in prison and a maximum fine of 100,000 baht.