Democracy protesters were set to return to the streets of Bangkok on Wednesday, a day after six of them were shot with live rounds, as lawmakers prepared to vote on possible constitutional reforms.
On Tuesday, in the most violent clashes since the pro-democracy movement kicked off in July, police used tear gas and water cannon on demonstrators.
Some in the crowd were shot, according to medical workers, though it was unclear who opened fire.
Bangkok has for months been rocked by youth-led rallies demanding a constitutional overhaul and the removal of Prime Minister Prayut Chan-O-Cha, who took power in a 2014 coup.
Some in the movement have also called for reforms to the monarchy -- a once-taboo subject.
On Tuesday, as lawmakers debated possible changes to the military-scripted constitution, protesters ploughed through police barricades towards parliament, prompting the use of tear gas and water cannon.
More than 50 people were injured, mostly by tear gas, according to the Erawan Emergency Medical Centre, an ambulance and medical coordination service, which said six people were shot.
Four people were still in hospital.
A Bangkok police spokesman denied officers had used rubber bullets or live rounds.
The Thai Human Rights Lawyers Association slammed the police tactics, saying "it was not in accordance with international procedure to disperse demonstrations".
At the two-day sitting, Thai MPs have been discussing various proposals for constitutional change, which mostly exclude any reform to the monarchy.
One proposal seeks to replace the military-appointed Senate with directly elected representatives.
It was Senate support that allowed Prayut to hold on to power after last year's election.
Parliament was expected to vote on Wednesday on which amendments are to be debated further.
The vote was expected to take several hours and may not be finished by the time protesters plan to regroup at Ratchaprasong at 4pm.
"We will open a new era in our fighting," prominent student leader Parit "Penguin" Chiwarak told the crowd overnight.
A heavy police presence was expected.
