That spine does protrude more than most pics I've seen and more than my BP's does.
However, I think the positioning of the snake in the pics might be part of what makes it look that way. What does he look like if he is just coiled on a flat surface? Like maybe find him in his hide, lift it off him & quickly snap a pic.
Anyway, I don't think he is dangerously thin. I've seen pics of newly rescued snakes that looked a lot thinner and recovered just fine.