Thailand's Kiradech Aphibarnrat admitted he paid the price for letting his mind wander to thoughts of a second European Tour title after a poor finish threw the Shenzhen International wide open.
Aphibarnrat fired nine birdies in his first 13 holes at Genzon Golf Club and held a six-shot lead with just two holes of his third round to play on Saturday.
However, the 25-year-old then ran up a double-bogey seven on the 17th and bogeyed the last to card a 68 and finish 12 under par, two shots ahead of playing partner Peter Uihlein.
Spain's Pablo Larrazabal was a shot further back on nine under, with English duo Tommy Fleetwood and Matt Ford, Argentina's Emiliano Grillo and Australian Scott Hend all firmly back in contention on eight under.
"I have been striking the ball so good the first few days," Aphibarnrat said in an interview on Sky Sports 4.
"Everything was going to plan, I tried to just keep the ball on the fairways. The way I played 16 holes was great golf.
"I missed a short bogey putt on the 17th, maybe thinking it was too easy, just knock it in. After hitting great shots on 15 and 16 I was thinking the game is done. I was trying to get a couple more birdies and lead by nine or 10 to confirm I can win tomorrow.
"I was striking the ball so good and rolling it great on the greens. I missed a few putts, but I am still in great shape. Just try to do the same thing tomorrow, go low and get the job done. It was a bad finish, but tomorrow is a new day."
Aphibarnrat got off to a flying start with birdies at the first three holes and made just one par in a front nine of 32 before holing from six feet for birdie on the 10th and chipping to within inches of the hole for another on the short par-four 11th.
Another birdie on the 13th took him four shots clear and that lead became six after Uihlein bogeyed the 14th and 15th, only for the 17th to change the complexion of the day when Aphibarnrat found sand with his third shot and compounded the error by three-putting from 15 feet.
Uihlein birdied the same hole to make it a three-shot swing and a par on the last was enough to get another shot closer to the lead.