"Thingy" is very informal, and it can also make it sound like you're deliberately trying to be cute. That's fine if that's what you intend; and if your listener agrees that whatever you're saying is, in fact, cute. If your listener doesn't find you and your use of "thingy" cute, though, then you just sound kind of dumb. You can take my word for it: I've done a lot of sounding dumb in English. ;)

yep