Seongnam climbed to eighth place in the K-League on Sunday thanks to a 1-0 win away at fourth-placed Ulsan.
A goal from Kim Seong-Jun just after the hour mark was enough to hand the visitors all three points at Munsu Cup Stadium, lifting Seongnam above Gyeongnam, who were held to a 1-1 draw at home to lowly Gangwon.
Serbian striker Milan Bubalo opened the scoring for Gyeongnam from the penalty spot in the 64th minute, but Romanian Ianis Zicu levelled - also from the spot - six minutes later to earn Gangwon a point that lifted them off the bottom.
And Busan I'Park needed a 92nd-minute goal from Lim Sang-Hyub to salvage a 2-2 draw from their visit to Chunnam Dragons.
Lim had given his side the lead just before the half-hour mark, but two goals in eight second-half minutes - a Hong Jin-Ki strike and a penalty from Brazilian Wesley - put the Dragons in front before Lim's late intervention ensured the honours remained even.