Scotty Nguyen is probably the most famous Vietnamese poker player. Though he's won unknown stacks his cash games, he's most famous for winning 5 World Series Of Poker bracelets since 1995. He won the main event in 1998, as well as the high roller 50K buy-in H.O.R.S.E event in 1998 and WPT (world poker tour) champion in 2006, being the only player to ever hit this trifecta.
Less famous but probably just as successful (or better), and much less extroverted, is Chau Giang. Chau plays and holds his own in the biggest cash games in the world. He's from a similar background as Scotty, who both fled from Vietnam to the USA with nothing, and made themselves playing poker. Both went broke several times and started again from scratch on their road to riches.
In any poker game involving women, the Viet chicks always own it. I remember watching a WSOP women's tournament event a few years ago where on the final table, 8 out of 9 finalists were Vietnamese, 3 Viet chicks took the podium, to spite there being less than 20% Vietnamese entrants. Possibly the best female player in the world is Mimi Tran. She knows her cards and is also a great meta-game player, fucking with all the white guy's heads. She doesn't havge the published tournament results of some other prominent female players, but Mimi plays in high stakes cash games that frighten most other ladys.
In poker you need to make general stereo-typical assumptions until you get more info on a player. The best assumptions are made by what the player does for a living, and their race or ethnicity. Lawyers play loose but cunning, Doctors play weak-tight, tradesmen make stupid wild plays, etc.
Thais are right up there with seppo niggas as the people you want at your table (provided they don't find a way to swindle you). They got a heap of gamble and none of the analytical smarts needed to beat the game. Jews are tough players but can't help talking all the time and give themselves away. Chinese are very good, but can't resist that big call with a marginal hand, and are very hard to bluff. Also tend to be superstitious. Scandanavians play way too loose. Poms whine when they lose hands and put themselves on tilt, etc.
So when you're in a game with a Viet or two, you know it's likely to be tough. I have no idea why this is, but they are definately disproportionately better than other races. They seem to have the right balance of fearless gamble and controlled risk, and seldom give away 'tells'. I've played with a fair few Viet players in both Sydney and Macau, and would definately be losing to them overall. In Macau, sometimes you can't tell if someone is Chinese or Vietnamese by looking at them, but when they start playing, you know.