Wesley Han, a non-binary actor famous for their work in "Power Book II: Ghost," is suing a swanky hotel in New York City for harassment and discrimination ... and it sounds like it's all about which bathroom they allegedly used.

In a new lawsuit, obtained by TMZ, Wesley claims they were attending a private event at the Soho Grand Hotel when they were accosted by a security guard who forcibly removed them from the women's restroom.

Wesley says they were dressed in women's clothing when they attempted to use the women's restroom ... and they say a security guard asked women in the foyer, "Excuse me ladies, have you seen a man enter?”

Wesley alleges the guard was told "no" but entered the restroom anyways and would not allow them to wash their hands. They claim the guard escorted them to the men's restroom, humiliating them in a walk of shame.

In addition to 'Power Book,' Wesley has also appeared on "Russian Doll" and "Awkwafina Is Nora From Queens" ... plus a big-screen role in "Paranormal Activity: Next of Kin."

Wesley is going after the hotel for damages ... claiming they suffered humiliation and emotional distress.

We reached out to the hotel ... so far, no word back.