The league leaders fell behind through Hassan Muftah's 29th-minute strike but drew level on the stroke of half-time thanks to Nam Tae-hee's penalty.
Nam scored from the spot again in the 64th minute and the hosts pulled away late on thanks to Ismael Mohammed (80) and Lassena Diaby (84).
Two goals from Rodrigo Tabata led Al Rayyan to a 3-1 win at Al Wakra.
Tabata opened the scoring from the penalty spot in the 25th minute, but Nashat Akram levelled two minutes into the second half.
Jaralla Al Marri put the visitors ahead for the second time after 70 minutes and Tabata rounded off the scoring in the last minute.