SINGAPORE - A mover who flouted train station rules by munching a sandwich on a platform slapped an SMRT service ambassador after he was told to stop eating.

Shafuan Juraimi, 22, was jailed for three weeks on Friday (Nov 30) after pleading guilty to assaulting 69-year-old Gian Cheng Kuan.

Deputy Public Prosecutor Tang Shangjun said that as a service ambassador, Mr Gian was tasked with ushering commuters, handling crowd control and enforcing SMRT regulations.

Shafuan was waiting at Raffles Place station with his colleagues at around 7.30pm on June 25 when they took out some sandwiches and started eating. Mr Gian walked up to the group and said: "Excuse me, no eating."

Shafuan and his colleagues kept their food and remained silent. He later opened a bottle and was about to take a sip when Mr Gian told him that drinking was also prohibited.

DPP Tang told District Judge Mathew Joseph: "On hearing this, the accused swung his right hand with the intention to hit the victim and then slapped the victim on the left cheek."

After that, Shafuan told Mr Gian: "I am really thirsty. Why I cannot drink. If I die, how?"

An eastbound train soon arrived and the group boarded it.

The police were notified at around 8pm and Mr Gian went to a clinic where he was given two days of outpatient medical leave.

DPP Tang urged the court to sentence Shafuan to three weeks' jail, stressing that the assault was unprovoked.

Before sentencing him, Judge Joseph told Shafuan: "The victim was old enough to be your grandfather and yet you had no respect for him. Your actions were utterly deplorable."

Shafuan, who was unrepresented, said that he was sorry and wished to apologise to Mr Gian.

For assault, he could have been jailed for up to two years and fined up to $5,000.