Bathing should be 1. On a need basis i.e if he has dirtied himself playing on the beach etc. 2. In general twice a month or even less frequently. 3. Incase of any special needs like skin allergy, foul smell a medicated bath in consultation with your vet.
Check with your vet if he has a medical condition, could also be due to Mumbai climate..to which many breeds can't adapt.