Security forces were deployed to disperse protesters early on Thursday
The Thai government has announced an emergency decree to combat protests in Bangkok, which includes banning large gatherings.
A televised announcement read out by police said “many groups of people have invited, incited and carried out unlawful public gatherings in Bangkok”.
It said urgent measures were needed to “maintain peace and order”.
Protesters have called for curbs on the king’s powers and for the resignation of Prime Minister Prayuth Chan-ocha.
The announcement on state television said protesters had “instigated chaos and public unrest”.
It cited protesters confronting a royal motorcade on Wednesday as a reason for the decree. The protesters, who were pushed back by ranks of police, raised the three-finger salute that has become a symbol of the protest movement as the queen was driven through Bangkok.
The emergency measures came into effect at 04:00 local time on Thursday (21:00 GMT on Wednesday).
In addition to limiting gatherings to four people, the decree puts restrictions on the media, prohibiting the “publication of news, other media and electronic information that contains messages that could create fear or intentionally distort information, creating misunderstanding that will affect national security or peace and order”.
It also allows authorities to stop people from entering “any area they designate”, Reuters news agency reports.
The growing student-led protest movement, which began in July, has become the greatest challenge in years to Thailand’s ruling establishment. Protests over the weekend in the capital were some of the largest in years, with thousands defying authorities to gather and demand change.
Authorities say 18,000 people joined Saturday’s demonstration, although others gave higher figures. Many stayed to continue the protest into Sunday before dispersing.
The protesters’ calls for royal reform are particularly sensitive in Thailand, where criticism of the monarchy is punishable by long prison sentences. (BBC).