32-year-old Chinnappa Vijayaragunatha Poopathi, a construction worker, had pleaded guilty on Friday to an amended charge of failing to disperse during the Little India riot on December 8 under Section 151 of the Penal Code.
It was believed to be the first time that Section 151 has been invoked in Singapore, Channel News Asia reported.
He was initially charged with rioting, punishable by up to seven years in prison and caning.
Deputy chief district judge S Jennifer Marie ordered Chinnappa's imprisonment to take effect from his arrest date on December 8, local media reported.
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Chinnappa and his friend, who were going to a canteen in Little India, ignored a warning by others that police had advised people not to go in that direction and leave the area. They had also consumed some beer, the report said.
Chinnappa could have been jailed up to two years and/or fined.
The trouble started after a private bus fatally knocked down an Indian pedestrian in Little India. Some 400 migrant workers were involved in the rampage that left 43 officers injured and 24 vehicles damaged.
Singapore previously witnessed violence of such scale during race riots in 1969.