A roti prata stallholder offered a friend who had come out of prison for drug-related offences not only a job but also a place to stay in his flat.

But the man, now 57, abused the stallholder's trust and betrayed his hospitality and charity by sexually abusing his seven-year-old son.

The accused chose to act because the child, who was in primary school, was frequently alone at home with him. On one occasion in December 2009, he forced the victim to perform oral sex on him.

He was jailed for six years yesterday after pleading guilty to one of three charges . Neither the accused, a married father of three, nor the victim can be named.

Assistant Public Prosecutor Dillon Kok told the court the accused worked for the victim's father at his roti prata stall after he came out of prison in 2009.

While he was home alone with the victimin December that year, he took the boy into a bedroom and committed the offence. The boy was too frightened to resist. After that, the accused gave the boy $5 and warned him not to tell anyone or the accused would have a "big fight'' with the victim's father and there would be a "big problem'' at home.

Sometime in late January 2010, the accused moved out of the flat.

Mr Kok said the accused's act came to light only in mid-2013 on an occasion when the victim asked his younger sister to stroke him.

The parents informed the police as well as the Ministry of Social and Family Development.

Citing several aggravating factors, Mr Kok said a jail term of at least six years was warranted to deter sexual predators who preyed on young, vulnerable victims.

He said the accused had sexually abused a child to satiate his lust, an act of the lowest level of depravity.

"When offenders commit such reprehensible crimes, they cannot expect to get away lightly. A stern and unequivocal message must be sent that there is no place in our society for such repulsive conduct,'' he said.

District Judge Jasvender Kaur said the fact that the accused had betrayed his friend's trust and the age of the victim were severe aggravating factors. She noted the duration of the act was about 20 minutes, and further, he had repeated the offence on two other occasions.

"The offence also had a lasting effect on the young victim,'' she said.

The accused, who has Parkinson's disease, could have been jailed for up to 20 years and fined for sexual penetration of a minor.