The manager of a karaoke pub, who slapped a singer so hard that she suffered mild hearing loss, had his jail term increased from 12 weeks to four months yesterday, following an appeal by the prosecution.

In enhancing the sentence meted out to Low Song Chye, the High Court laid down sentencing guidelines for cases of voluntarily causing hurt - an offence which carries a maximum of two years' jail.

In his written judgment, Justice See Kee Oon devised three sentencing bands based on whether the harm caused was low, moderate or serious.

Those who commit offences involving low harm, with no visible injury or with minor hurt such as scratches and abrasions, will face indicative sentences ranging from fines or short jail terms of up to four weeks.

At the other end of the scale, assailants who cause serious injuries that are permanent or require significant surgical procedures will face indicative jail terms of between six months and two years.

The sentences will be adjusted depending on relevant factors specific to each offender.

In the current case, Low had claimed trial to causing hurt to Ms Guang Man by slapping her face and ear, and grabbing her neck, in the early hours of July 12, 2016, at a MacPherson Road karaoke pub.

Ms Guang - whose job included singing, drinking and inducing customers to buy flower garlands - had gone to the pub's office to collect her salary, as it was her last day of work.

However, she was dissatisfied with the amount offered and refused to accept the money.

After exiting the office, she picked up some balls from a pool table and threw them around.

Ms Guang testified that Low had grabbed her neck and slapped her with "very great force" on the left side of her face and her left ear, and told her to stop throwing tantrums.

Low, who was responsible for security at the pub, denied assaulting her. His version of events was that he had gone up to Ms Guang to stop her from throwing the pool balls, but she had become aggressive.

He said his hand had come into contact with her cheek - but that he had used "not that great" a force - as he was pushing her away.

A medical examination found that Ms Guang's left eardrum was perforated.

Low was found guilty by a magistrate's court last year and sentenced to 12 weeks' jail. He was also ordered to pay Ms Guang $800 in compensation.

He appealed against the conviction, sentence and the compensation order, while the prosecution appealed for a harsher sentence.

Yesterday, Justice See said Low's case fell into the moderate harm category and that four months' jail was appropriate, considering his past violence-related antecedents.

However, the judge said: "While the accused's actions were certainly disproportionate and unwarranted, there was also an element of provocation by the victim."

Low's appeals were dismissed.