Austria's Markus Brier remained the leader of the Commercialbank Qatar Masters presented by Dolphin Energy after nine holes of his third round in Doha.
Ranked 478th in the world and without a top-20 finish on The European Tour last year, Brier turned for home one ahead of Dane Thomas Björn.
The 42 year old was a relieved man to find his ball on the long opening hole after carving his second shot into the trees, but then came birdies at the fourth and sixth thanks to ten foot putts.
However, the 639 yard ninth cost Brier a bogey six after his approach from the rough flew over the green.
Former Ryder Cup star Bjorn, 40 later this month, followed his second round 65 with birdies at the first and seventh in an outward 34.
That took him past South African Darren Fichardt, out in 36, while defending champion Robert Karlsson and double US Open Championship winner Retief Goosen both fell back.
Karlsson, joint third overnight, double-bogeyed the second and totally duffed a chip at the short eighth to drop to 13th.
First round leader Goosen double-bogeyed the eighth just as he had the 17th on Friday and on two under had six strokes to make up.
In contrast, 2009 winner Alvaro Quiros, who started with a 75, was up into a tie for fifth and five under for the round with one to play.
Quiros picked up another shot at the par five last - he needed only a drive and nine iron to reach the green on the 548 yard hole - to set the clubhouse benchmark at six under.
“I'm very happy,” said the 28 year old. “Obviously to shoot 66 on a golf course like this, even when we have the easiest day, is a great thing.
“I still have the feeling that I can reduce this score a little bit more, but I have to be happy. It's going to give me the chance to be tomorrow in the top ten for sure and have a little chance, depending on what the leaders make.”
Brier pitched to three feet on the 11th, and when he converted another ten foot chance at the next he was suddenly three clear at ten under.
Björn quickly cut that back to two, though, with a third birdie of the day on the 14th.