Something like 1 in 4 transgender women are also autistic. If this study holds any water that might be an interesting investigation.
If someone publicly asserts they're trapped in the body of the wrong sex, and does not back down when challenged, might this be sufficiently weird to be ASD by definition? Especially given the awkwardness of violating gender norms.
A comparison between ASD diagnosis rates in places where trans identity is culturally normalized might shed some light on it, but as ASD diagnosis is also pretty cultural it might be tricky.