
Metropolitan Police commissioner Lt-Gen Suchart Muenkaew said eight companies of police, in all 1,200 strong, would be on duty, with a further nine companies in reserve.
Salang has threatened to retake Government House from the People's Alliance for Democracy (PAD).
Suchart said he believed violence would be avoided because of royal ceremonies related to the upcoming cremation of HRH Princess Galyani Vadhana but that if police could not control the situation, he would seek reinforcements from the Army.
"We have a lot of experience, so there should be no worries about our ability to control the situation. We will be in control," Suchart said.
Salang has threatened to use a "special weapon" to deal with the PAD-led protesters.
Suchart said he had not been informed by Salang what that weapon would be, but he believes a certain procedure is necessary before Salang could deploy it.
On reports that some active policemen would join Salang's crusade against the PAD, Suchart said he had no objections to their joining any demonstration led by Salang outside of duty hours.
"If they want to demonstrate as unarmed as citizens, they can, but they'll be prosecuted if they carry guns," he said.
Suchart admitted he could not prevent Salang from entering Metropolitan Police headquarters to express moral support for the police, as Salang used to be his superior and mentor.
He said Salang had a perfect right to organise campaigns but that there would be no official police participation, adding that active police officers had never even attended Salang's press conferences.
Suchart said the Metropolitan Police had been negotiating without success with the PAD to end the blockade of Rajdamnoen Avenue at the Makkhawan Bridge, because the road would be needed for royal ceremonies.
On Tuesday, the PAD opened the road and said it would rally only inside Government House but moved in again on Thursday for security reasons.