Thomson also stopped immediately behind the victim and hopped out of his car.
Armed with a half a pool cue, he approached the other driver, who was still sitting in the driver's seat, and remonstrated with him before striking him in the face.
The left side of the victim's face was bruised.
When police visited Thomson's Te Puke address with a search warrant on November 2 they found a cannabis-growing room in a bedroom. It showed signs of recent use.
Inside was a tent and frame which took up the majority of the room, a carbon filter, a fan, ducting, lights, fertiliser, and about 200g of cannabis plant material commonly known as cabbage.
Thomson told the police that the victim had put his children in danger and that he had been growing tomatoes in the grow room.
His lawyer, Whare Hika, urged Judge Thomas Ingram to further remand his client on bail because Thomson was due to start a new job on Monday and had five young children.
Judge Ingram said he normally would not do so given the circumstances, particularly when this was not Thomson's first conviction for violence.
Thomson was remanded on bail for sentencing on January 15.
The judge urged him to talk to the probation officer and to "have a good think" about how he got in this position, and what he planned to do to rehabilitate himself.