Thornton needed just a single blow to find the cup at the 198-yard 11th and that provided one of two eagles as the 36-year-old fired a six under par 65 in windy conditions.
"That was obviously pretty good," he joked on www.europeantour.com. "I just played really well, hit some good shots and in weather like that you just have to keep straight and that's what I do well."
His round left him four under for the tournament going into tomorrow's final day and was good enough for a share of the lead along with South African Tjaart van der Walt and Frenchman Baptiste Chapellan.
"I was making greens and giving myself chances and I managed to take them today [Saturday]," Thornton added.
"The weather suits me, I like playing in a breeze.
"There were times when you could have hit any one of five clubs because the wind was unpredictable, but you just have to pick one and trust it.
"I holed about a 30-footer for eagle at the ninth and then the hole in one.
"I was in between a seven iron and an eight iron and I hit a nice smooth seven and it was all over the flag, one big bounce and it just rolled in, it was really good shot.
"There were a few high fives and shouts, it was my first one in a professional tournament so I was delighted."
Van der Walt started the day in a share of the lead and an up-and-down round which contained an eagle and a double-bogey saw him maintain that position with a 71.
England's Robert Dinwiddie had also shared the lead overnight but five bogeys in his 74 saw him fall three shots off the lead.
Chapellan hit three birdies on his way to a 69 to claim a share of top spot with Englishman Steve Benson one shot behind after carding a 70.
German Max Glauert, England's Chris Lloyd and Frenchman Victor Riu were all a further shot back on one under.