The toddler identified as Mohammad Bilal was playing with his sister and a cousin, both five years old, in the bedroom under the supervision of his mother, according to the local daily New Straits Times.
The fatal accident is believed to have happened when the mother left the room briefly to answer a phone call from her husband and Mohammad entered the bathroom, the report added.
On her return, the mother found the child's lifeless body with his head submerged in a half-full bucket of water.