Okini in Osaka

Hello, I read on Reddit that okini can be used to say thank you in Osaka. Since this is specific to this location, I am now in Osaka and use this word diligently.

Often, the person I'm talking to is surprised at first, and they often giggle.

Now I'm not sure if they're smiling at me or laughing at me.

Is it okay to say okini, and if so, in what situations is it appropriate?

One final question—what can I say colloquially to say goodbye?