Kinhult is six under at the halfway stage with England's Chris Wood in second at four under, a shot clear of Spanish world number five Jon Rahm and Welshman Bradley Dredge, the overnight leader.
World number two Justin Thomas is two under alongside fellow American Julian Suri, England's Matthew Fitzpatrick and France's Gregory Havret.
The French Open is taking place at the Saint-Quentin-en-Yvelines venue which will stage the Ryder Cup from September 28-30 and when Europe will attempt to reclaim the trophy from the United States.
After finishing third at the Qatar Masters in February, unheralded Kinhult had made just three of eight cuts since. The 21-year-old had started his first round on Thursday with four straight bogeys but went ten under for his next 32 to become the first player to start with four dropped shots and hold a 36-hole lead since records began in 2000.
“It feels good, it feels really good,” he said. “I got off to a great start and played well from there. The wind picked up a little bit on the back nine, the last four or five holes or so, but happy overall. Saturday is going to be a big day and hopefully Sunday as well. It's a position I have never been in before so we'll see.”
Thomas birdied the third, 11th and 15th but he found the hay on the left of the 17th, missed the green and failed to get up and down in surrendering a double-bogey.
“Man, it was one of the better rounds I've had in a while. I could have shot a 1-under on the front easy, could have shot a three or four under,” said the American.