A court acquitted him in December, after the golfer claimed he had no memory of his actions because he had drunk alcohol and taken sleeping tablets.
Olesen had been ranked 62nd in the world but his best finish this year is 12th from seven starts on the DP World Tour.
Fox was the co-leader after the first round but slipped back to 10th after the second. He opened his third round with a bogey, and immediately rebounded with birdie.
But the Kiwi couldn't get a run going and finished even for the day, although he was helped with his third birdie of the tournament on the par five 17th.
Olesen, who shot three under par on the third round, has a three shot advantage over German Hurly Long and England's Marcus Armitage.