Police on Saturday issued a reminder to social worker Jolovan Wham about his plan to hold a demonstration on Sunday at the Speakers' Corner.
A spokesman said in a statement on Saturday that police are aware of Mr Wham's plan to hold a demonstration "to show solidarity with groups of Malaysians who are against the Malaysian General Election".
"In the same invitation, he had invited foreigners to observe the event," said the police. "Police have reminded (Mr Wham) that while he is free to organise and speak at a demonstration at Speakers' Corner, it is his responsibility as organiser to take appropriate measures to ensure that the our laws are complied with."
In Singapore, a police permit must be obtained before foreigners can participate in a planned demonstration at the Speakers' Corner.
"The Speakers' Corner is a designated site for Singaporeans to freely speak on issues as long as they do not touch on matters which relate to religion or may cause feelings of enmity, hatred, ill-will or hostility between different racial or religious groups in Singapore," added the police,
"Only Singaporeans and permanent residents of Singapore are allowed to participate in demonstrations held at the Speakers' Corner."