score:3
Smoking 10 meters within bus station [in Gyeonggi-do], (10 meters within) subway station exit[in Seoul and Gyeonggi-do], any places with this sign, most public restrooms, 강남대로 [Gangnam Daero] in Seoul, all government-related buildings, restaurants, bus/train, medical facility, will result in KRW 100000 (about US$100) fine.
Basically, look for the sign, and avoid smoking in public if you are near subway station exit/bus station and in Gangnam.