In a rare move, a judge has labelled the prosecution's argument for a sentence as lenient.

Deputy Public Prosecutor Yvonne Poon had argued for chef Adrian Chen, 30, to be sentenced to 18 months in jail for threatening a woman with a cleaver. He had placed it against her neck in a public place. The DPP said it was an aggravated case of intimidation.

In judgment grounds last week, District Judge Kenneth Yap said it was a fair position but to his mind, "leans on the side of leniency".

He noted that the charge involved a threat to cause death or grievous hurt, which carries a maximum 10-year jail term and/or a fine.

Judge Yap said: "It would not do for offenders to whip out household knives to threaten innocent third parties in crowded public areas."

Chen, who had pleaded guilty to criminal intimidation in threatening Madam Lim Thi Tuyet Hong, 42, was also given a concurrent sentence of two weeks' jail for punching her face.

At around midnight on Sept 25 last year, Madam Hong witnessed Chen arguing with his Vietnamese girlfriend, Ms Le Thi Phuong, outside the restaurant that Madam Hong owns in Joo Chiat Road, and intervened.

After his girlfriend left in a cab, Chen took out a chopper with a 15cm-long blade from his sling bag, and confronted Madam Hong.

He pushed her to the ground. After she stood up, he placed the knife against the left side of her neck, uttered a threat and punched the right side of her face, prompting patrons at her restaurant to step in and evict him.

Madam Hong called the police after Chen returned 40 minutes later.

She had bruises and abrasions and received outpatient treatment the next day.

Arguing for the 18-month sentence, DPP Poon pointed to past precedents, including the 2002 case of a senior police officer who was jailed for three years for threatening a supermarket manager with his service revolver after being detained for shoplifting.

Chen's lawyer, Mr Kalidass Murugaiyan, pointed to mitigating factors, arguing that Chen acted on impulse and was prepared to undergo counselling.

Judge Yap said the prime consideration must be the nature of the threat and the extent of alarm engendered in the victim.

Noting that Chen was "clearly prepared to get his way" by using the chopper, the judge added that "perhaps the most serious consideration must be the environment and surrounding context".

"The sense of alarm is magnified when the threat is made in public, at a restaurant where other patrons are also within arm's reach of the accused," Judge Yap said.

Chen, who is out on bail of $25,000, is appealing.