At NK primarily, one way I had brought the "East" into a standard western Europe styled campaign setting, was to have a large city with a China Town located within it as immigrants from the East settled into this large urban sprawl.

It was great way to bring ninja, monks, samurai and other eastern flavored classes into a "normal" D&D world, without forcing the party to travel East to see it. I know in some senses this reflects a more modern setting, however, think of Baghdad of pre-medieval period with many other cultures having followed the trade routes including: Chinese, Jews, Africans, Russians, Mongols.

Its really not that hard to imagine Eastern classes in a standard D&D world, if you look at that example.

GP