Thailand's government invoked a special security law on Thursday before a massive anti-government rally planned for tomorrow.
Nearly 17,000 police officers will be deployed at the rally which officials fear could turn violent.
The security act allows authorities to close roads, impose curfews and ban use of electronic devices in designated areas.
Hundreds of thousands are expected in what is likely to be the biggest opposition rally since PM Yingluck Shinawatra took office in 2011.
The demonstration is being organised by royalist group Pitak Siam at Bangkok's Royal Plaza.
Led by retired army General Boonlert Kaewprasit, the group accuses Yingluck's government of corruption, ignoring insults to the monarchy and being a puppet of former prime minister Thaksin Shinawatra.
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