Lee struck with just seven minutes to go as Pohang claimed their fifth win of the season in which they remain unbeaten.
It was a timely struck given the form of Suwon Bluewings who claimed a 4-1 win at Daejeon Citizen with a hat-trick from Jong Tae-se.
However, it was the hosts who took an early lead from Lee Wong-hee in the eighth minute but that was as good as it got as they were ahead for just 10 minutes when Jong levelled.
He got his second goal eight minutes later before Stevica Ristic effectively ended the game as a contest when he pounced on the stroke of half-time.
Jong completed his treble two minutes from time as they kept up the pressure in second place.
Lee Hyo-kyun scored twice in the last two minutes as Incheon United moved into third following a 3-1 win over Jeonbuk Motors.
Lee Seung-gi gave Jeonbuk a 29th-minute lead with the home side levelling through Diogo Acosta's penalty six minutes after half-time.
The game appeared to be heading for a draw before Lee Hyo-kyun struck for the first time in the 88th minute and confirmed victory in the final minute.
FC Seoul enjoyed their first win this season as they demolished bottom side Daegu FC 4-0.
The match was over with less than half an hour having been played with Ko Yo-han (16), Mauricio Molina (20) and a Dejan Damjanovic penalty (28) giving them an unassailable lead.
Molina scored his second seven minutes from time.