South Korea would be the same as any other country except Canada. Have the South Korean CAA verify your license, complete an ATP CTP course if you want a ME ATP, pass the written test and pass a checkride. If you take the checkride in an airplane you would need at least a FAA third class medical. No medical is required to take a checkride in a sim but to take the checkride in a sim you would have to complete a training program at a part 142 training center even if you have that type rating on your Korean license.