Until the East was opened up to the west (maybe the last hundred years or so?) both Japanese and Chinese traditional music used forms of the pentatonic scale much like what we use, although the temperament of the tuning was different. This is why in old Charlie Chan movies the music uses what Tommy S. has described (You can get a sad sounding asian-like scale by playing the black keys only, but always landing on Eb instead of Gb). This is most effective if the melodies are played over a root/5 drone with no changes, to firm up the pentatonic sound. But let's get away from cultural stereotypes and realize that if you want to make music that sounds "asian", the best way is to listen to the actual music of the culture you are trying to emulate. All countries and cultures have diverse and rich musical traditions that too centuries to develop, and simply playing a pentatonic scale and calling it "asian-sounding" is not going to cut it. Get out there and listen to some other cultures' music and you will be surprised what you can learn. There can be no doubt that Cambodian, Vietnamese, Chinese, Japanese, Burmese, and Malaysian music (among others) are all dramatically different, and expressive of their own culture's struggles and triumphs.