1) Are you an ethnic Korean?
If yes, get a F-4 visa (if you are eligible) and 1000 hours total. If not, forget about it.
2) Do you have S.Korean nationality?
If yes, get 1000 hours total time. Be it from CFI hours or whatever. If not, forget about it.
3) Still wanna work for KAL?
If yes, get jet times and then apply as an expat through agencies. However don't forget the no.1 above. Ethnic Koreans cannot apply for KAL positions through agencies despite you holding another country's citizenship.