Again, I prefer collections with both vocal and instrumental cuts. My favorite is "Deep in a Dream: The Ultimate Chet Baker Collection". Great song selection. "Grey December" is another good one. If you want actual albums with nothing but vocal tracks, "Chet Baker Sings" is the obvious choice (haven't heard it but know some of the songs and it's pretty popular). There's also a collection called "The Best of Chat Baker Sings" that might be the way to go.
You also might wanna make sure his vox are to your liking, because they're kind of an acquired taste. Here's his most well-known vocal track (famously aped by Matt Damon in "Talented Mr Ripley"). Definitive version of a great song IMO: