The overnight leaders Brett Rumford and Westwood have found the going more tough.
Starting the round on 8-under, both missed the second cut and failed to reach Sunday's match-play stage of the tournament.
Former world No. 1 Westwood struggled all day with wayward driving and heaved his club in frustration after teeing off into the bush on the 14th. A birdie burst after the turn saw him make four par breakers in five holes from the 11th and that meant he could absorb bogeys at 13 and 18.
"Not a lot went my way", Westwood said.
"Not a lot went my way; that's how it goes sometimes", he said. "I hit a few bad shots, got a few bad breaks, never made any putts. You're not going to score well doing that".
Rumford was the defending champion, having won the qualifying stage by five strokes past year.
"I'm happy to have signed for 72", Rumford said.
"It's a long day". Bidding to back up Liam Johnston's win in the Open Prestigia, the first leg of a double-header, earlier in the week, Howie had gone into the last day just a shot off the lead but ended up three adrift as Frenchman Julien De Poyen claimed the title. It's hard to get any kind of rhythm or momentum or anything out there.
"You would have to lie to say that you're not aware of your opponent, but I'm not playing against (Westwood), I'm not changing my game plan or swing thoughts or nothing, I'm just playing golf".
Thailand's Prom Meesawat took the top seed by finishing on 12 under, two shots ahead of Sean Crocker of the United States, Australian Lucas Herbert and Dane Thorbjorn Olesen.
NSW's Dimitrios Papadatos was the biggest mover, pushing through the field to be in a tie for fifth spot at 8-under after carding a 6-under 66 for the round. "Finish the stroke play rounds in first place, and then win the tournament", added Prom, whose last matchplay experience in his professional career was in 2007, in a team event that pit Asian golfers against their European counterparts.
The leading 24 players after three rounds will qualify for the six-hole knockout matchplay.
All of the top four held the lead at some point during the day, but nonetheless start on a level footing on the final day.