I randomly came across this website, which may be of interest to you in your research:
http://www.asianamericansonbroadway.com/home.html A few other Asian actors that came to mind:
Mako - Pacific Overtures (Tony nom).
Miyoshi Umeki - Flower Drum Song (Tony nom).
Pat Suzuki - Flower Drum Song.
June Angela - Tuptim in the 70s revival of King and I, Shogun the Musical (Tony nom).
BD Wong - M. Butterfly (won Tony), You're a Good Man Charlie Brown, the short-lived Face Value
Alec Mapa - M. Butterfly.
Baayork Lee - A Chorus Line, Promises Promises, others
Francis Ruivivar - Shogun the Musical, Engineer in Broadway Miss Saigon (the first Asian-American in the role)
Barry Bernal - original Thuy, Broadway Miss Saigon
Kam Cheng - original alternate Kim, Broadway Miss Saigon, ensemble in King and I
Joohee Choi - Tuptim in King and I revival
Jason Ma - Thuy/Engineer in Miss Saigon
Luoyong Wang - Engineer in Miss Saigon
Leila Florentino, Roxanne Taga, Rona Figueroa - Kim in Miss Saigon
Margaret Anne Gates - Ellen in Miss Saigon
(There are a lot of other actors that were cast in Miss Saigon over the years - the ones above are just the ones that came to mind. I'm sure you can find a list somewhere).
If you want to talk about leading/featured Asian roles, you should be sure to touch upon the handful of other Asian-themed Broadway shows, including Pacific Overtures, Flower Drum Song, South Pacific, M. Butterly and Shogun the Musical (in addition to Miss Saigon and the King and I, which you already mentioned). There aren't that many so you can't really ignore any of them. There are also some smaller Asian roles in a few shows, including Avenue Q, Thoroughly Modern Millie, Chorus Line and Asian actors have been cast in smaller roles in You're a Good Man Charlie Brown, Mamma Mia, City of Angels, Company, Rent, etc.
Beyond Broadway, you may want to take a look at off-Broadway, including the Pan Asian Rep and other companies that specialize in productions starring Asian actors or Asian themed shows. And you should see if you can read Yellow Face, David Henry Hwang's latest play at the Public, which was a Pulitzer finalist this year and discussed the issue of Asian actors and non-traditional casting.
Good luck!
"This is wanting something, this is reaching for it,
This is wishing that a moment would arrive.
This is taking chances, this is almost touching, what the beauty is." --The Light in the Piazza