The Chief of Defence Forces, General Chalermpol Srisawat, signed the order on Friday prohibiting people from holding rallies or public gatherings in Bangkok, Samut Prakarn, Samut Songkhram, Nonthaburi, Nakhon Pathum, and Pathum Thani provinces without approval from officials.
People who violate the order will face two years' imprisonment, or fine up to Bt40,000, or both.
Four pro-democracy groups and one pro-monarchy group have scheduled rallies in Bangkok on Saturday.