The national police chief is proposing the government use the Internal Security Act (ISA) to contain the anti-government protest planned by the Pitak Siam group in Bangkok on Saturday.
Pol Gen Adul Saengsingkaew said he would propose to the National Security Council (NSC) Monday that it implement the security act to cope with the rally.
Use of the act, if approved, would empower the prime minister to order soldiers to bring the rally under control to maintain security.
Police fear Boonlert Kaewprasit, addressing the last Pitak Siam rally, may not be able to keep his word about a peaceful protest on Saturday.
Police will monitor the rally but will not obstruct the demonstration with checkpoints, Pol Gen Adul said.
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He said his police force is still collecting information about the rally and did not yet have an estimate on the number of demonstrators likely to attend.
Meanwhile, pro-government red-shirts rallied in Bangkok Sunday to oppose Pitak Siam's plan of forcing the government to step down.
Red-shirt leader Sombat Boonngam-anong led about 100 participants on a protest against Pitak Siam at Bangkok's BTS train system.
The protesters told people at the Siam Square and Chatuchak stations that Pitak Siam's intention to oust Yingluck Shinawatra's government would "freeze" elections in Thailand for five years.
The protesters said those who oppose the government should fight in parliament under democratic rules.
Mr Sombat said red-shirt supporters would launch more activities to oppose Pitak Siam's protest.
He said red-shirt demonstrators in Nonthaburi province would rally in front of the Thaicom satellite earth station on Saturday to oppose Pitak Siam's rally, which will be held the same day.
A group of university students called the Group of University Students Who Love Democracy, rallied at the Democracy Monument in Bangkok to express their disapproval of Pitak Siam.
Thailand's reputation would be harmed if the elected government is overthrown, Nanthasak Poolpol, who led the group, said.
He said Pitak Siam's stance would be a violation of the parliamentary system. His group distributed stickers opposing what they called an attempt to "freeze Thailand".
Meanwhile Gen Boonlert Kaewprasit, the leader of the Pitak Siam movement, launched caravans of vehicles at the Royal Plaza yesterday to urge people to join his rally on Saturday.
Gen Boonlert said Pitak Siam had no intention of "freezing" Thailand, but instead wanted to freeze the country's corrupt politicians.
He declined to elaborate on what that could include.
Gen Boonlert reiterated the government is a failed proxy of ousted prime minister Thaksin Shinawatra.
He said the government tolerates corruption and offences to the monarchy.
Ms Yingluck's government had come to power as a result of populist vote-buying, Gen Boonlert said, adding that Pitak Siam would demand the resignation of the government.
He said he would end the movement if it fails to get support from a targeted number of people.
Democrat Ong-art Klampaibul said yesterday the government had tried to counter Pitak Siam by accusing the movement of accepting money from a political party.
The government also tried to quell the rally by announcing the deployment of 50,000 police.
Neither tactic will work, Mr Ong-art predicted.