I started a publication-order read through (skipping any Dark Tower entries and saving them for the end) a while ago, and i have made it half-way through Four Past Midnight (1990), so I will limit my recommendations to his earlier works.
I love all his short story/novella collections, but if i had to pick one to recommend it would probably be Different Seasons, though Skeleton Crew is up there as well.
For the novels, a few of my less well-known or less commonly recommended favorites (in publication order, since i’m looking at my e-reader history) are The Dead Zone (especially poignant in the current state of politics), Roadwork (very compelling story of a guy’s refusal to come to terms with a changing world), Christine (the premis sounds dumb, but he really pulled it off), The Eyes of the Dragon (his foray into fantasy), and The Tommyknockers (this along with Cujo were written deep in his cocaine days and it shows, but i couldn’t put it down and some of my favorite King moments are in this book).
Any of his well-known ones are fantastic too (a general rule to follow is: if they’ve made a movie, especially if it was a bad movie, it’s gonna be a good read), but I’m gonna shout out The Shinning in particular. The book is very different than the movie; not plot-wise per se, but the character development is so much deeper and more multi-dimensional. If you’ve seen the movie but haven’t read the book, you don’t really know The Shinning. No shade against the movie being thrown here, I love them both but for very different reasons.
In the interest of stopping before I list his whole bibliography, I’ll end by saying you can safely add any of the Bachmann books to your list, especially since you liked Thinner.
It really is a quintessential example of “you can’t judge a book by it’s cover”