BANGKOK — Earlier this week, 22-year-old Parit “Penguin” Chiwarak found himself huddled with several other activists from his university in the small two-floor townhouse they live in, debating, planning and exchanging ideas.

There was lots to discuss, he said, ahead of a planned rally Saturday, set to be among the most significant in their growing pro-democracy movement. This time, the student activists planned to take their fight to Thammasat University, their campus — and the nearby royal grounds.

“I slept for only two hours last night; we talked until 5 a.m.,” Parit said in an interview, boxes of goggles lying by his side, prepared in case police were to fire tear gas, along with walkie-talkies, microphones and amplifiers. “There are many things that we need to prepare.”

He added: “This will be a milestone in our declaration of war against the dictatorship. Six years ago, they declared war against the people by staging a coup. Now, it is time to declare we are fighting back.”

By midafternoon Saturday, despite the pouring rain, a police raid on the same townhouse hours earlier and warnings from authorities, thousands of Thais answered their call to protest for greater democratic rights.

They raised their hands in a three-finger salute from the Hunger Games trilogy, now a symbol of resistance. They carried signs denouncing the military and the government. And they shouted chants calling for changes to the constitution and fair elections, a key demand of the movement.

“Where I live, everyone has fundamental rights,” said Napat Kulruchakorn, a 21-year-old computer sciences student at the University of Southern California. In Thailand, he added, “people are threatened because of their opinions.”

At the center of this movement, growing bolder in its demands for political and monarchical changes, is Parit and his fellow students, some so young they have not finished high school. Once dismissed as radicals, the students have spearheaded one of the biggest mass movements in Thailand in years, posing a once-unthinkable threat to the kingdom’s political institutions — including the powerful monarchy.

“I think young people have the power to make change,” said Veeranuth, a 62-year-old retiree. “I’ve put my hopes on them, because they are fighting for a better future. I want to show up here, and support them.”

Protesters on Saturday planned to camp out on the university grounds overnight before marching to government house to deliver a petition. Thammasat University, where Parit studies political science, is nestled on the banks of Bangkok’s Chao Phraya River, next to the expansive royal grounds — gilded, manicured compounds that to them exemplify monarchical excesses.

Police closed roads leading up to the royal grounds, as well as the Grand Palace, as hundreds more arrived at the rally by the hour. Officers patrolling the area warned people they may be in violation of the kingdom’s criminal laws as well as laws controlling the spread of the coronavirus, and urged participants to leave. Protesters jeered in response.

For Parit, the reasons for the growing dissent are obvious. Though Thailand is a constitutional monarchy, the palace retains wide-ranging powers and is deeply embedded in the economic and cultural fabric of the country. Amid yawning economic inequality and a disputed election that extended the term of the junta chief who took power in a 2014 coup, the present King Vajiralongkorn was crowned, having taken the throne after the death of his revered father, King Bhumibol Adulyadej, in 2016.

“The wind changed when the reign shifted” between the two kings, Parit said. The election, he added, made clear to Thais that they could speak out against the anti-democratic shift in the country and be supported.

“Once the train leaves, you can’t stop it,” he said.

Risks have been mounting for Parit and other young activists since they decided to expand their movement to take aim at the entirety of Thailand’s political elite, breaking a taboo in the country against open criticism of the monarchy. Thailand has among the strictest lèse-majesté laws in the world, punishing disrespect of the monarchy with up to 15 years in jail. Even in coffee shops and conversations at home, Thais have long used nicknames to refer to the king or use pop culture references to subtly signal dissatisfaction with the system.

That changed over the summer when the students, who had been leading the catchall democratic movement, took a stage to openly challenge the monarchy, rewriting the boundaries of public discussion in Thailand. The decision, Parit said, was six months in the making, part of heated late-night debates and discussion among the university students.

“We all know that the monarchy is at the center of Thailand’s political conflict, and we have positioned ourselves on the front line of the democracy movement,” he said. “If we aren’t brave enough to start this discussion, who will? It is our duty to do that.”

After that speech in August, the activists expected their friends and allies to distance themselves, wary of the risk of association with the students. But, Parit said, they were delivered a “new life” instead.

“It is like we were the very first people to fly over the clouds, where we could see the beauty and brightness that lies above,” he said. “So we have a mission to tell people how it is like up there. We must tell them the monarchy is not a subject for private gossip, but that they can speak out. Everyone can.”

At the demonstration Saturday, some held signs directly mocking the king and his outfit choices, as well as the significant time he spends in Germany. Others called for people to remember what happened at Thammasat University some 44 years ago — the massacre of student activists just like Parit on the campus lawn, some gunned down, some hung by their necks on tree branches. Official figures say 46 died, but activists say that number is probably higher.

Parit, who was arrested in mid-August and released on bail, faces 18 charges so far, everything from violating cleanliness laws to sedition. He is aware of the consequences of his activism, he said, and does not fear persecution — only sometimes reminiscing of the days he spent poring over archived records of the ancient Lan Na kingdom in northern Thailand, what he describes as a bit of an obsession, and dreaming of his alternate life as a historian.

“I guess this is the price I have to pay for my activism,” he said with a laugh.

And as the sun set over a rain-soaked Bangkok on Saturday, thousands sat gathered, their eyes focused on the stage in front of them, waiting for the 22-year-old and his fellow student activists to speak.

Mahtani reported from Hong Kong.