SINGAPORE - A security guard was sentenced to four weeks' jail on Tuesday (Oct 25) for punching a bus captain.

Sia Siong Ing, 55, pleaded guilty to punching SBS Transit bus captain Sivanandan Ponusamy, 41, on the right cheek at the basement 2 bus bay of Terminal 3, Changi Airport, at about 12am on Oct 17, 2015.

The court heard that Sia boarded a bus along Tampines Avenue 5 and took a seat behind the driver, who noted that Sia smelled of alcohol.

As the bus was approaching the bus bay of Terminal 3, Mr Sivanandan applied his brakes gradually until the bus came to a complete stop.

By this time, Sia had stood up from his seat. As a result of the bus coming to a stop, he swung forward while holding on to a pole, but did not fall.

Sia scolded Mr Sivanandan and continued to do so after getting down. The victim responded in kind.

Sia then walked to the driver's side window and gestured towards the victim. At Sia's request, Mr Sivanandan opened the window. Sia threw a punch on the driver's left cheek. Mr Sivanandan sought help from members of the public to call the police.

He held on to Sia until police arrived.

Sia, who had a similar conviction in 1996, could have been jailed for up to two years and/or fined up to $5,000 for causing hurt.

He was allowed to start his sentence on Nov 1.