For a sec there I thought he was shedding lol but it kinda doesn't look like it.
Soak him in warm water for a good 10-20 minutes daily. While he bathes he'll soak up some of it through his skin and also drink some of it. Give him clean, fresh water daily as well.

The thing I do with my snakes if I don't see them drinking (I stay up ALL night now.. and I know all of them roam around) during the day or the night then I will take the snake and put his/her head up the water and sometimes let their front lip touch the water and they will drink the water while I'm holding them up to it.