I know there are more than at least 50 different Korean actors that played non-speaking and speaking parts. My question is, who are the actors that played different characters throughout the series, and what parts did they play.
You're right; there were many actors of Asian decent that played roles on episodes of M*A*S*H. Many of them were not of Korean decent specifically but either Japanese or Chinese. Here are a few:
1. Mako - He was a frequent guest star on many episodes including the N. Korean doctor arranging a wounded prisoner exchange in "Rainbow Bridge" from season 3, The S. Korean soldier trying to take a captured woman in "Guerilla My Dreams" from season 8 & many others. By coincidence he was married in real life to Shizuko Hoshi who was also a frequent guest on many M*A*S*H episodes, such as the mother in "Hawkeye" from season 4.
There were many others such as Jack Soo from "Barney Miller" fame & Rosalind Chao who later was Soon Lee Klinger.
Hope this helps.
Yours in M*A*S*H,