Enraged after his father refused to hand over $2,000, a student stabbed the older man multiple times with a knife.
Dylan Loy Zhong Huan, 19, pleaded guilty in court on Wednesday to causing grievous hurt to his father, Mr Loy Shiang Chian, with the weapon.
The court heard that the teenager had been living with his grandfather since Nov 18, 2016. Court documents did not state the reasons behind this arrangement.
Before that, Loy had been asking his father for money, claiming he needed $3,000 to pay for Uber rides as part of a "survey".
Mr Loy, 49, transferred $1,000 to his son's bank account.
After spending it, the teen asked his father for $2,000, but the older man refused to give him any more cash.
On Nov 29, 2016, Loy asked his grandparents for the money at about 6am but they also rejected his request. He then took a steak knife with an 8cm-long blade and went to his father's flat in Bishan.
Mr Loy was leaving home at about 8.30am when he spotted his son hiding beside a shoe cabinet.
Loy confronted his father and demanded to know why he did not give him the money.
He then pushed the older man.
He next grabbed his father's key pouch and flung it towards a drain in the corridor.
As his father tried to retrieve it, Loy took out the knife and stabbed him in the back of his head two or three times.
Deputy Public Prosecutor Michelle Lu said: "The victim screamed for help and tried to stop the accused from using his key to enter the unit.
"However, the accused continued to stab and slash the victim... and he also punched and kicked the victim multiple times."
Mr Loy's neighbour, who heard the commotion and saw the scuffle,alerted the police.
An ambulance took Mr Loy to Tan Tock Seng Hospital, where he was treated for multiple stab wounds. He was discharged two days later.
On Wednesday, District Judge May Mesenas called for reports to assess Loy's suitability for probation and reformative training.
Offenders sentenced to spend time in a reformative training centre follow a strict regimen that includes counselling.
Loy is expected to be sentenced later this month. For causing grievous hurt with a weapon, offenders can be jailed for up to 15 years and fined or caned.