He has seen his father smoking and drinking. The child wanted to do his father's work in his absence. Why father should beat him with belt? It is completely a wrong doing by the father. If he thinks drinking and smoking is not good, at least he should not do those activities in the house. If he really thinks that these are bad habits he should stop that activity. But without doing that punishing the child is a offence.
The action of the father reveals that he knows what he is doing is wrong and he don't want his son to do that. Ok . His intention may be correct. But his actions are not proper. Father needs to be punished.