The National Legislative Assembly voted overwhelmingly on Thursday in favour of a bill that restricts political demonstrations, something critics fear will be used to smother dissent after martial law is lifted.
The law will impose restrictions on the "time, place and manner" of demonstrations but it was not aimed at banning protests, said army spokesman Winthai Suwaree.
"This law is not designed to prevent protests. It is aimed at giving order to public gatherings," Col Winthai told Reuters.
Currently, martial law bans public gatherings of more than five people. It was imposed two days before the May 22 coup after months of street protests aimed at ousting former prime minister Yingluck Shinawatra.
Critics say the law on restricting protests that sailed through its first reading on Thursday would help the current military regime to stifle dissent.
"This law will replace martial law and control political protests which infringes on people's rights," said Thanawut Wichaidit, a spokesman for the United Front for Democracy against Dictatorship group.
The bill must pass a second and third reading for it to become law, which parliament watchers said is likely given its support in the NLA, whose members were picked by the military.
If the bill becomes law it would ban protests outside courts, parliament and the prime minister's offices, Jate Siratharanont, a member of the assembly, told Reuters.
Police would have to be informed of a protest at least 24 hours in advance and gatherings between 6pm and 6am would be banned unless protesters got permission, Mr Jate said. But authorities would need permission from the courts to disperse protests.
Matthew Smith, executive director of Fortify Rights, a Southeast Asia-based rights group, said it would be difficult for Thailand to argue that the law was in the public interest.
"On the contrary, this appears to be a move that's inconsistent with Thailand's human-rights obligations," said Mr Smith.