"I was hitting my drives very nicely today and if you're hitting the drives well here you can make a lot of birdie opportunities because it is not an extremely long golf course," he said.
"I had quite a few short birdie putts out there and I didn't make every single one of them but I'm happy I made four of them and didn't make any bogeys."
The winner of the FedEx Cup, found after the Tour Championship, will take home a bonus cheque for US$10 million.
Meanwhile, Lee has made it no secret this season he has been gunning for a spot on the International Team competing at the President's Cup in October in South Korea, his country of birth.
His form this season has lifted him just inside the cut to make the International Team.
"I'm right inside the President's Cup, I'm No10 right now," he said.
"So I'm really focusing on that and just trying to hang on to that last spot as much as possible for the next couple of weeks and, hopefully, I'll get in."
Lee needs to be in the top-10 eligible players for the International Team on the Official World Golf Ranking to make the team.