A man was sentenced to 24 weeks' jail on Monday for assaulting a bus driver who told him to cover his nose and mouth with the mask he had tucked under his chin.

Shake Mohammed Abdul Samad Haji Abduraheem, 46, scratched 28-year-old Mr Low Chun Kiat's face and pulled down the bus driver's mask. He also pulled a bus control lever, causing nearly $1,500 in damage.

Abdul Samad had earlier pleaded guilty to one count each of assault, harassment and committing an act of mischief that caused disruption to a key service.

On Feb 16, at around 1.15pm, Abdul Samad boarded service 334 at Jurong East Bus Interchange while wearing his mask under his chin.

Mr Low then reminded Abdul Samad to wear it properly.

Deputy Public Prosecutor Kenny Yang said: "The accused responded by asking if he should wear his mask covering his chin, mouth, his eyes or above his head.

"At about 1.20pm, the complainant noticed the accused was still not wearing his mask properly and reminded (him) to do so."

Abdul Samad then called Mr Low a "donkey" and abused him with vulgar language.

The driver stopped the bus near Block 490 Jurong West Avenue 1 and told Abdul Samad to remain seated. Mr Low then called his superiors to ask for police assistance.

Abdul Samad tried to alight from the bus, pushing past the driver to do so.

DPP Yang said: "The accused then reached for the bus control located at the driver's seat and the complainant attempted to stop him. In the struggle, the accused pulled down the complainant's face mask and scratched him on the face. The accused also pulled on the complainant's left ear during the altercation."

Mr Low sought treatment at Ng Teng Fong General Hospital, where he was found to have injuries including swelling on his left ear.

For assault, an offender can be jailed for up to three years and fined up to $5,000. For committing an act of mischief causing disruption to a key service, an offender can be jailed for up to 10 years and fined.