20 May 2014 Last updated at 15:32 BST
The Thai army has imposed martial law "to preserve law and order", granting the army sweeping powers to enforce its decision.
Both pro and anti-government protesters have been told not to march anywhere in order to prevent clashes.
The move comes amid a political crisis and after months of escalating tensions. It could enrage supporters of the government, especially if it is seen as amounting to a coup.
Here is the background to the crisis - in 60 seconds