Prime Minister Prayut Chan-o-cha on Thursday declared that "all laws and all articles" will be enforced against protesters who break the law.
Prayut gave his warning after street rallies by pro-democracy protesters demanding his resignation, as well as reform of the monarchy.
He said the government and various agencies had tried to find a peaceful way out of the conflict.
However, the situation has showed no sign of easing, Prayut said.
"The situation is not easing and there is a tendency for conflict to escalate into more violence. If not addressed, this could cause damage to the country and the beloved institution, as well as to peace and the safety of people's lives and property," Prayut said.
"It is necessary for the government and security agencies to intensify their actions by enforcing all laws and all articles to take action against demonstrators who break the law and show no respect for the rights of other people," he said.
Many thousands of pro-democracy protesters descended on Ratchaprasong intersection during their huge rally on Wednesday night.
Expletives were painted on walls and on roads during the rallies. The People's Movement protesters announced the next rally will be on Nov 25.
