I researched on this over a decade ago. I was going to do a Hmong dating website, but as my research concluded, I realized that women are too shy to reveal anything about themselves. And the guys, well, most of them would be the predator type (married/cheaters/one night stands). I even thought of the possibility of charging for membership as that would deter the non-serious daters. But of course, Hmong people are pretty cheap too, so it just would never work out. Decided not to waste my time on the dating site. Fast forward 10+ years, and it's still the same.
There are some dating sites out there that Hmong men and women join, but usually they're looking for people outside the race. Good luck!