His mother, Azlin, told police she did not intend to kill the child and argued she was too small to be able to do it.
"How am I able to kill a child? Just look at my small body," she reportedly told police three days after the boy's death.
"I do not have the intention to pour the hot water on him if he did not show any attitude towards me," she said in another statement.
In a police interview, she said she "only wanted him to learn his lesson".
"If I had the intention of killing him, I would have killed my other children as well," she reportedly said.
"But all my other children are safe and I do not beat them. As a mother, I would not have the heart to kill my own child."
Photos of the boy's injuries, including burns and cuts to his body, were shown on a screen in court.
A pathologist testified that even the boy's gums were torn.
His list of injuries also includes third degree burns covering about 75 per cent of his body, acute kidney injuries, dehydration, a broken nose, and cuts on his face.
He also suffered from isolated speech delay.
He died a few days after being admitted to hospital.
According to prosecutors, in August 2016, the boy knocked over a biscuit tin and his mother beat him so violently his stomach had marks. He also reportedly began to hobble due to a misaligned kneecap.
When the child "stole" milk powder to eat, the father allegedly placed a scorching metal spoon on the youngster's palm.
He died on October 22, 2016. That day, the boy was allegedly confined to the cat cage.
He reportedly refused a bath and his mother called his father to discipline him. He allegedly poured hot water over the boy's back and calves.
The parents reportedly waited six hours before taking the boy to hospital.
If found guilty, the parents could receive the death penalty.
The trial continues.
