Because there’s not enough work here. Or, there’s work, but it’s difficult to get many hours, and the pay is pretty bad.
I’ve heard things are better in Phenom Phen, the Cambodian capital, but the basic trouble is just that Cambodia’s starting to feel the pinch, and there’s not a lot of money going around.
Anyway, if you want a good free Korean language course, this is the one I’ve found:
the FSI (Foreign Service Institute) Korean language course, by Unit
the FSI (Foreign Service Institute) Korean language course, by Volume
BTW, it’s shockingly expensive to fly to Korea from Cambodia — as much as it would cost me to go home! What’s with that?