BANGKOK: Thousands of high school students upset about Thailand's lacklustre education system rallied alongside protestors dressed as dancing dinosaurs in Bangkok on Saturday. It was the first mass gathering in the kingdom since Prime Minister Prayut Chan-o-cha warned authorities would use all laws, including harsh royal defamation charges, to crack down on pro-democracy protesters.

Since August, emboldened by a broader political protest movement sweeping Thailand, a group called the "Bad Students" have campaigned for the resignation of Education Minister Nataphol Teepsuwan, demanded cultural change, equality, a curriculum overhaul and relaxation of strict rules.

Ahead of Saturday's rally three student leaders were summoned for police questioning and Thai Lawyers for Human Rights said there were now four juveniles facing potential prosecution.

But despite the threats the youngsters remained defiant as they danced alongside half a dozen T-Rex characters representing Thailand's "political dinosaurs" and bounced around giant "asteroid" balls.