I read an article about The Big Sleep(1946) where they had to hint at the sexual exploits of Carmen Sternwood because censorship wouldn’t allow them to say that she’s been doing pornographic photo shoots. So they put her in a “Chinese dress in a Chinese chair" as innuendo. During that period in Hollywood, people understood that "Chinese" was code for "immoral or deviant". Anyway, point is, mentioning "Chinese" was supposed explain that she did porn.

So, when Jensen says “I’m coming over” and “I want in”, the joke here means that if she brings up the word “Chinese”, then she could be sexually adventurous enough to be into threesomes.

Side note: He couldn’t have been referencing the Chinese Swing/Sex Swing because it wouldn’t make sense in the context of Jensen “wanting in” (unless he wants to borrow it)