Korea isn't like the states. They have LOTS of pool rooms and Koreans love to gamble. I was there about a year ago & it seemed like there were pool rooms every block. Granted, a lot of them are 3-cushion rooms. But walk in to any room & ask for a room popular for pocket billiards & they'll point you in the right direction. I'd assume there's a good room or two near the military bases (camp Humphreys), so that might be a place to start. That district has great shopping & awesome food, lots of bars & some nice hotels, so if you get tired of pool there's plenty other stuff to do.