An appeal by prosecutors to increase the sentence of a teenager who beat up two foreign workers was dismissed yesterday by Chief Justice Sundaresh Menon.

In April, Daryl Lim Jun Liang, 18, was given a 10-day short detention order for causing hurt.

Lim and three others assaulted two foreign construction workers - an Indian and a Chinese - in Yishun last year. They had prowled the estate looking for smaller-sized foreign workers to pick on.

Lim was ordered to report to a supervision officer every day for a year, remain indoors from 10pm to 6am for a year, and perform 150 hours of community service.

The other teenagers are Tan Jun Liang, 18, and two 15-year-olds who cannot be named because of a gag order. Tan's case is pending, while the two others have been given 18 months' probation. Lim had earlier pleaded guilty to one charge of voluntarily causing hurt.

Yesterday, Deputy Public Prosecutor Francis Ng urged the court to pass a stronger deterrent sentence and send Lim to the Reformative Training Centre, saying that the teen displayed a "penchant for fighting" and had gone into the encounter last year "prepared to fight".

After Lim was sentenced, Law Minister K. Shanmugam called his actions "completely unacceptable".

"It's sickening conduct," he said.

Yesterday, Lim's lawyer Luke Lee noted that his client has been assessed to have a low risk of re-offending and is due to be called up for national service next month.

CJ Menon took those factors into consideration and noted that it was not Lim but his accomplices who repeatedly punched the construction workers in the face.

CJ Menon said the detention order was a "short, sharp shock", and ordered Lim's parents to pay a bond of $10,000 to ensure their son's good behaviour.

He told Lim: "The court is taking a chance that you can yet mend your ways and grow up to be a responsible citizen."