Ahn Yong-woo opened the scoring just after the hour and Stevica Ristic put the hosts up 2-0 11 minutes later. Santos pulled one back 12 minutes from time, but Ahn's second goal of the game in the 89th minute sealed matters. The result left third-placed Suwon nine points behind leaders Jeonbuk Motors after 21 matches, and lifted Chunnam to fifth.
Also on Sunday, bottom-placed Gyeongnam picked up only their third win of the campaign with a 3-1 success at Sangju Sangmu Phoenix. Sreten Sretenovic's early opener was cancelled out by Lee Keun-ho's 34th-minute equaliser, but Sretenovic struck again after the break and then Milos Stojanovic rounded things off.
And Busan I'Park moved up a place to third-bottom at the expense of Seongnam Chunma courtesy of a 4-2 triumph at their relegation rivals. Lim Sang-hyub's goal and a Jose Fagner penalty had the visitors in the ascendancy before the break and, although Kim Dong-hee halved the deficit on the hour, two goals in two minutes - from Lim and Ju See-jong - pulled Busan clear. Server Djeparov grabbed a second for Seongnam in the final minutes but it was too little, too late.