Anti-government white mask members of the V for Thailand movement on Sunday gathered in front of the CentralWorld shopping complex and in many provinces, as well as overseas, to show dissatisfaction with the administration of the government under Prime Minister Yingluck Shinawatra.
About 600 policemen from Metropolitan Police divisions 4, 5 and 6 were deployed to maintain law and order at the Ratchaprasong intersection.
Before the rally started, Metropolitan Police deputy chief Thitirat Nonghanpitak said the situation would be assessed on an hour-to-hour basis to decide whether to call for police reinforcements or whether to propose the imposition of the Internal Security Act.
Police will try to prevent a possible clash between the white mask group and a pro-government group and watch for any interference by a third party, Pol Maj Gen Thitirat said said.
CentralWorld department store management used steel barriers to block an area in front of the mall to prevent the white masks taking up too much space.
According to an initial plan posted in the V For Thailand website, after gathering in front of CentralWorld the demonstrators would then march to the Bangkok Metropolitan Administration's (BMA) arts and cultural centre where they would sing the national anthem before dispersing.
The white masks were also planning similar demonstrations, mostly from 4pm, in many provinces such as Nonthaburi, Suphan Buri, Uthai Thani, Nakhon Sawan, Sing Buri, Lop Buri, Saraburi, Prachin Buri, Prachuap Khiri Khan and Ratchaburi in the Central Region.
In the East, the white masks planned to rally in front of Central department store and Lotus department store in Pattaya as well as in the muang districts of Rayong and Chanthaburi.
In the North, they planned to rally in Kamphaeng Phet, Phetchabun, Mae Hong Son, Phitsanulok, Lampang, Chiang Rai and Lamphun.
In the Northeast, they planned to rally in Ubon Ratchathani and Buri Ram.
In the South, the white masks were to hold a similar rally in Chumphon, Nakhon Si Thammarat, Phatthalung, Phuket, Narathiwat, Pattani, Yala, on Koh Samui and in Ban Don districts of Surat Thani, Krabi and Satun.
The V For Thailand website reported that the white masks had also rallied at Belmore Park and Central Railway Station in Sydney, Australia, and in Hong Kong.
Suriyasai Katasila, Green Politics group coordinator and an anti-government activist, said the government was afraid of the white mask movement.
Mr Suriyasai said groups of people in different countries, such as Brazil and Turkey, are wearing Guy Fawkes masks to protest against their governments. The Thai government was feeling shaky and was trying to intimidate people from joining the movement, he added.