"We estimate that more than 20,000 people attended today," a member of the Free Youth movement, a student-led organization behind the protest, told Sputnik.
The organizers gathered over 19,000 signatures under a petition calling to rewrite the constitution, which was created while the military was in power from 2014-2019.
The police said that some 12,000 people had turned up, but the counting was made within a confined perimeter of the square where the main rally was held and did not include thousands thronging nearby streets.
The demonstrators called for the resignation of Prime Minister Prayut Chan-o-cha and the parliament's dissolution to pave the way for a new government that would be free from the military clutch.
"We, the youth, should rethink the ways our forefathers lived by. We realize we can no longer live under a dictatorship whose powers are enshrined in the existing constitution," a speaker said from the tribune.
In what was unthinkable only a few years ago, the protesters demanded that the monarch's powers be limited. A rival rally of Thai king's loyalists was held nearby but their numbers were underwhelming.
