Two goals from Kim In-han (14 and 50) sandwiched a Rocha Caique strike as Suwon fell to their fifth loss of the season.
They remain three points behind Jeonbuk and a point behind second-placed FC Seoul.
Busan I'park failed to break into the top five with a last-minute 2-1 defeat against Incheon United.
Han Kyo-won fired Incheon ahead after 57 minutes with Yoon Dong-min equalising in the 78th minute.
However, a last-minute goal from Jung In-whan sealed the win for the visitors, who move out of the bottom three as a result.
Sangju Sangmu Phoenix climbed off the bottom with a 1-0 victory over Pohang Steelers, courtesy of Kim Min-woo's early strike.
Seongnam Chunma and Chunnam Dragons shared a 1-1 draw. Ju Sung-hawn's opener for Chunnam was cancelled out by Hong Chul.