PAM will kill all stages of the mites that are on him. It will last for 30 days in a small dusty residue in his cage that the mites will come in contact with and will die from this.
Just spray the cage down, before spraying the cage besure to remove the snake and water bowl and wait about 1 min to air it out. Return the snake when you feel comfortable, but wait 1 hr to return the water.