Don’t Keep it Casual
The Western culture is considerably more casual than that of Eastern Asia. There are, however, some parallels between the two. We generally use a doctor’s or teacher’s professional title and last name when talking to doctors and instructors in the West. However, almost everyone refers to their bosses simply by their first names at work.
Korea is a country where everyone strives to exhibit respect for one another, and avoiding referring to individuals by familiar titles is one way to keep this mentality. Doctors must be addressed formally by their title and name, even in casual social gatherings, much as they are in the West.