BANGKOK -- Protesters gathered Saturday in Bangkok for the most ambitious rally so far in a pro-democracy campaign that has shaken up the government and Thailand's conservative establishment.

Organizers predicted that as many as 50,000 will march over two days in an area of the capital historically associated with political protests, after an estimated 10,000 people turned out for the last major rally on Aug. 16. But the early turnout was modest Saturday as a steady light rain fell.

Demonstrators wore face masks, but ignored a Thursday night plea from Prime Minister Prayuth Chan-ocha to cancel the event, which he said risked spreading the coronavirus and derailing recovery of Thailand's battered economy.

The core demands declared by the protesters in July were the dissolution of parliament with fresh elections, a new constitution and an end to intimidation of political activists.

They believe that Prayuth, who as then-army commander led a 2014 coup toppling an elected government, was returned to power unfairly in last year's general election because the laws had been changed to favour a pro-military party. A constitution promulgated under military rule is likewise undemocratic, they charge.

The mostly student activists raised the stakes dramatically at an Aug. 10 rally by issuing a 10-point manifesto calling for reforming the monarchy. Their demands seek to limit the king's powers, establish tighter controls on palace finances and allow open discussion of the monarchy.

Their boldness was virtually unprecedented, as the monarchy is considered sacrosanct in Thailand. A lese majeste law calls for a prison sentence of three to 15 years for anyone found guilty of defaming the royal institution.

The students are too young to have been caught up in the sometimes violent partisan political battles that roiled Thailand a decade ago, Kevin Hewison, a professor emeritus at the University of North Carolina and a veteran Thai studies scholar, said in an email interview.

"This is why they look and act differently and why they are so confounding for the regime," Hewison said. "What the regime and its supporters see is relatively well-off kids turned against them and this confounds them."

At least 8,000 police reportedly were deployed for the weekend protest, and prospects for confrontations appear high. Protest organizers have been said they will use Thammasat University and the adjacent field known as Sanam Luang as the rally venue, but had been denied permission to do so.

Undeterred, a small group pushed and argued Saturday at one of the university gates until it was opened, with no resistance from the authorities. Later, protesters began assembling a stage in Sanam Luang, despite police warnings that they were breaking the law.

"I cannot accept a system that is corrupt, but with the last few rallies there was no response from those who hold the power," said one protester, Thanakorn Thatana. "The three core demands were ignored and even the most basic demand to stop harassing the people. The government didn't listen to us, but instead there was an increase in harassment cases against even primary school kids."

Arrests on charges including sedition for earlier actions have failed to faze the young activists.

Students launched the protest movement in February with rallies at universities around the country in reaction to a court ruling that dissolved the popular Future Forward Party and banned its leaders from political activity for 10 years.

The party won the third-highest number of seats in last year's general election with an anti-establishment stance that attracted younger voters, and it is widely seen as being targeted for its popularity and for being critical of the government and the military.

But public protests were suspended in March when Thailand had its first major outbreak of the coronavirus and the government declared a state of emergency to cope with the crisis. The emergency decree is still in effect, and critics allege it is used to curb dissent.

Royalists have expressed shock at the students' talk about the monarchy. Army commander Gen. Apirat Kongsompong indirectly but harshly criticized the protesters, declaring in a speech to military cadets that "COVID-19 can be cured ... but the disease that cannot be cured is the hatred of the nation."

But actual blowback so far has been minor, with only halfhearted organizing efforts by mostly older royalists.