Is it normal to want to masturbate into thongs/panties?

Just don't evolve into a serial killer and you will be fine.

I steal them and wear them and cum in them

I have a similar habit. In my case, however, the women are still wearing the thongs or panties.

cum in a girl/woman's clean panties and put them back in the drawer

tes, i luv 2 cum in panties

damn yes, it is normal. i think most guys want to smell a woman's panties