My male is like that - can feel spine and hip bones. However I think he is naturally thin.

I worm regularly and feed high meat food (Bozita). What I have found helpful is getting him weighed regularly at the vets - it is free and they have a weighing machine specifically designed for weighing animals! The nurses do it.

I try to get him weighed every 4 months or so and note his weight each time for my own records but also it gets put on his vet record.