Is it possible that he has a skin infection like ringworm, or lice? Either of these could cause him to smell unpleasant and would not be solved by normal baths. Try an insecticidal shampoo for dogs, and wash his bedding in a hot washer cycle as well. Ringworm (fungus) would need something from the vet.
The other possibility is that he has found something lovely to roll in and keeps going back to it.
The other possibility is that he has found something lovely to roll in and keeps going back to it.
