Ultimately, you can’t know someone’s aversion until you ask, and that can be a personal question. My advice is, when in doubt, don’t make the joke.
Asexual joke, What's an asexual person's favorite thing to do in the bedroom?
Five asexual people are playing cards
Every month if you're married.
Asexual joke, When is Asexual Pride Month?
Asexual reproduction is reproduction with only one party