The wrinkly skin means he'll be shedding soon, in all likelihood. Many chams are difficult to observe drinking water. If you don't see your Cham drinking, just check his urates (the white "cap" that often comes with the poop). If it's white then it's reasonable to conclude your Cham is hydrated. Yellow or orange and the Cham needs more water. How are you currently getting water to your chameleon? Hand misting? Automated mist system?