Years ago I lived in Malaysia in a home near a rubber plantation. Frequently we found cobra's (black not king) in our yard. The Indian guard (Hindu) we employed would not kill them since he was concerned they may be relatives re-incarnated. I cut down all the oil palms in the yard to discourage frogs which the cobras were eating. Upon advice of the old Malaysia hands, I sprinkled powdered sulfur around the yard. This seemed to help the problem. However, before sprinkling sulfur it was necessary to insure all the snakes were out of the yard since they would not cross the sulfur to get out of the yard. Knew an older English man there who came into Burma during WW II and he told me they used sulfur to repel snakes in the Burma jungle.