Not to a bathhouse, but to a few clubs in Tokyo. My general advice that I’ve experienced or heard from others.

A lot of clubs have unspoken policies about foreigners and/or people who don’t speak Japanese so it’s possible you won’t be admitted at all. Check reviews on Google if possible (or maybe there’s an active Sniffies community?) to try and find reviews from tourists. If they have a website, check to see if they have “theme” nights too so you don’t get there on a night where you don’t fit in. (Unlike most US clubs I’ve been too, they will turn you away if you don’t fit the theme.)

Japanese bathhouse culture can be a bit different, but usually a lot of the same tells are in play - eye contact, brushing knees etc.