Jolovan Wham, 37, appeared in court accused of organising three small protests between November last year and July.
These were a candlelight vigil outside a prison for a death row convict, a protest on a subway train and a demonstration at which a Hong Kong democracy activist spoke via video link.
Police described Wham in a statement as "recalcitrant" and said he had "repeatedly shown blatant disregard for the law".
While it is one of Asia's safest and wealthiest countries, Singapore has faced criticism for its tough laws.
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People convicted of organising such protests face a fine of up to 5,000 Singaporean dollar (USD 3,713). Repeat offenders must pay up to 10,000 Singaporean dollar, face a maximum six-month prison sentence, or both.
The subway protest saw Wham and several blindfolded activists ride on a train while holding up books in protest against a 1987 security operation in which 22 people were arrested under a tough law that allows for detention without trial.
Wham was also charged with one count of vandalism for pasting protest posters on a metro train and three counts of refusing to sign statements he made to the police.
Phil Robertson, deputy Asia director at Human Rights Watch, said Wham's prosecution "demonstrates the absurdity of Singapore's laws on public assemblies and the government's willingness to penalise those who speak out.
"The Singapore government should start listening to criticism, stop treating peaceful assemblies as crimes, and cease prosecuting their organisers.
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