A Thai woman runs into a wall, what breaks first? Her boner
Why do you think this type of joke is funny? Does it have to do with stereotypes about Asian people?
It is not a stereotype and it is funny because they can't hold an erection.
You shouldn't make jokes that suggest all Thai people are transgender. It implies that there is something wrong with transgender people, when there isn't. Transgender people are a lot more visible in the media, so maybe you can read about them to form a different opinion.