Singapore authorities charged human rights activist Jolovan Wham on Wednesday for organising public assemblies without a police permit, prompting rights groups to call on the government to guarantee the right to peaceful assembly.

The 37-year-old Wham, the former executive director of a group advocating the rights of foreign workers in Singapore, could be fined up to SGD10,000 or imprisoned for up to six months, or both, if found guilty of repeat offences.

Wham was involved in a protest in June by several blindfolded activists who held up books on a subway train in a call for justice for 22 people detained in 1987 under a tough internal security law.

"Wham is recalcitrant and has repeatedly shown blatant disregard for the law, especially with regard to organising or participating in illegal public assemblies," Singapore Police Force said in a statement.

He was also charged for vandalism and refusing to sign statements made during investigations, the police said. He faces a total of seven charges stemming from public assemblies he organised dating back to Nov 2016, the police said.

Under strict public assembly laws, protests are allowed only at a designated downtown square called the Speakers' Corner.

Human Rights Watch on Wednesday called on Singapore to drop the case against "peaceful protestor" Wham and to amend what it called a "draconian" law on public order to guarantee Singaporeans the right to peaceful assembly.

"Prosecuting Jolovan Wham for holding peaceful gatherings demonstrates the absurdity of Singapore's laws on public assemblies and the government's willingness to penalise those who speak out," its deputy Asia director Phil Robertson said.

"The Singapore government should start listening to criticism, stop treating peaceful assemblies as crimes, and cease prosecuting their organisers," he said.

A pre-trial conference for the case will take place on Dec 13.

- Reuters