A 32-year-old Indian national was sentenced to 15 weeks in jail on Monday for his role in last December's Little India riot - the first among 25 accused to be dealt with.
Chinnappa Vijayaragunatha Poopathi, who was originally accused of rioting, pleaded guilty last Friday to an amended charge of continuing to be in an assembly after it had been ordered to disperse under Section 151 of the Penal Code.
Deputy chief district judge S. Jennifer Marie ordered Chinnappa's imprisonment to take effect from his arrest date on Dec 8.
He could have faced up to two years in jail and/or a fine, as opposed to up to seven years in jail and caning for rioting.
This is believed to be the first time that Section 151 has been invoked in Singapore.
The Dec 8 riot was the worst case of violence Singapore has seen in more than four decades. It left 49 Home Team officers injured and 23 emergency vehicles damaged.