Re-hydrating a snake via tubing can be done easily but if you never have before, I suggest you have a qualified vet do it. Since the air passage is separate there is not much chance of you doing it wrong but don?t take a chance call a vet.
Also check the eye caps for signs of dehydration. If wrinkled it needs more moisture.
My thoughts would be if your snake got to this condition once it might happen again if there is not a change in your husbandry practices.
First is your humidity what it should be for that species?
Does your snake have a water bowl big enough for it to soak in?
Is your snake so large that when it climbs over the edge of the water bowl is it putting pressure on its esophagus making it hard to drink?
Now the most important of all, do you clean and change water daily? Snakes have an ability to know when water gets stagnant and will not drink it.
A full water bowl will be left alone even if the snake is thirsty. Snakes need fresh water daily. Even survival manuals given to army personnel tell to drink water where snakes drink from, chances are it is clean. God just programmed them that way. So please, clean and change water daily. I even go so far as to place my snakes in the water bowl as I fill it and I see them drink often.
Good luck
Hugs and Hissessss,
Maria