Hundreds of masked high school students demonstrated in Bangkok over the weekend to demand reform of an education system they say is outdated.
It was the latest in more than a month of anti-authority protests.
Protests that began on Thai university campuses have taken place almost daily since mid-July in an increasing challenge to the government in the Southeast Asian country.
Many protesters are also demanding changes to the powerful monarchy.
Students rallied outside the education ministry in Bangkok, calling for the freedom to be able to speak their minds at school and the relaxation of rigid rules on uniforms and behaviour.
“Thai education has made us puppets,” 18-year-old Supicha “Menu” Chailom said. “We are not robots of the system; we are the youth and have the right to express ourselves.”
Protests spread to some high schools last month, with students raising the Hunger Games movies’ three-finger salute during morning assemblies, a symbol of the pro-democracy movement.
Education Minister Nataphol Teepsuwan told reporters that he respected students’ rights, according to Reuters.
“The issues that the youth raised are things we can come to an understanding on as long as we respect each other and the rules,” he said.
Prime Minister Prayuth Chan-ocha, the main target of the protests, warned protesters they were creating divisions that could cause the collapse of Thailand and leave it “engulfed in flames”.
He has particularly condemned those who have demanded reforms to the monarchy – traditionally a taboo subject.
Thailand’s lese-majeste law, which forbids insulting the monarchy, is among the strictest in the world.
It has been increasingly enforced ever since the Thai military took power in 2014 in a coup, and many people have been punished with harsh jail sentences.
Last week, Thailand’s government released a cartoon drawn by King Maha Vajiralongkorn, who spends most of his time in Europe, that portrayed a happy Thai family living a contented rural life.