I agree answer the questions in the link above... from the looks of him he is very sick though and I could throw several things out there. But generally he will likely need to go to the vet.
The eye is not only shut it's swollen and sunken in a bit. Could be a number of things going on there.
The lip sticking out indicates the possibility of a mouthninfection starting...so mlook inside the mouth along there.
The legs are thin so it's indicating that it needs to be eating more.
Vet might be the best option...and be aware that they can crash quickly...so ASAP is the best option.
If you answered the questions we might have more answers.