He missed Jimmy Green's 54-hole tournament record by one shot after he came in at 15-under-par 198 at the TPC Wakefield Plantation.
'To increase my lead after shooting 2-under, I'm pretty fortunate,' acknowledged Thompson, who has held at least a piece of the lead after all three rounds. 'I'm really surprised nobody made a push from behind.'
Bob Burns stayed in second place on Saturday after a 1-under 70. He completed three rounds at 11-under-par 202, which is two strokes better than David McKenzie, who fired a 7-under 64 to get to third place at 9-under-par 204.
Thompson was up and down through the front nine with two birdies and a bogey. He bogeyed the 10th, but luckily, no player made a significant move toward his lead.
On the second nine, Thompson closed strong with a birdie at the par-3 14th, and a birdie at the par-5 closing hole.
'I shot a different score, but I hit the ball as well today as I did the last two days,' said Thompson, who only missed four greens in regulation on Saturday. 'I hit it great. The only difference was the putts didn't go in.'
This marked the sixth time Thompson has held at least a share of the 54-hole lead. He has yet to visit the winner's circle, but seems to have a strong game plan for Sunday.
'I've had so many close calls that it's been frustrating,' said Thompson. 'It just feels good to be playing good golf again. I'm looking forward to the final round. I'm going to attack the pins and make birdies. My game plan will not change at all. It is like playing chess, just make one move at a time and not get ahead of yourself.'
Aron Price (67), Tom Carter (71), Rick Price (72) and Tommy Biershenk (71) are knotted in fourth place at minus-8.
Keith Nolan (68), Scott Dunlap (68), Keoke Cotner (70), Garth Mulroy (70), Mario Tiziani (70) and Tee McCabe are tied for eighth place at 7-under-par 206