A Bangladeshi construction worker, Ray Chandan, 37, pleaded guilty to two counts of outrage of modesty.
A third count of molestation involving a 15-year-old girl was taken into consideration during sentencing.
According to TNP, Ray usually molested his victims between Yishun and Khatib stations, as the train would be more crowded at this stretch – making it easier for him to stand close to them.
At around 6.50am on May 11, he boarded the train at Sembawang station with his first victim, who was wearing her school uniform.
The 17-year-old girl stood behind him and kept herself occupied with her mobile phone.Seeing that the girl was engrossed with the device, Ray molested her.The girl looked down and saw his knuckle touching her private parts over her clothes.
When she stepped back, he moved towards her and continued committing the offence.
The girl then decided to snap his picture before alighting at Yio Chu Kang station.
She lodged a police report at around 10.20am that day.
He had also admitted to molesting a 15 year old girl when finally caught by the police.