Coles, an Australian, had a 71 to tie Singh at 11-under 205.
Singh, a 42-year-old Fijian, tied the course record of 64 Thursday. He trailed Coles and Quigley after two rounds.
Singh, earned his 25th career win earlier this year and was voted into the World Golf Hall of Fame earlier this week.
"I'm quite happy with my position right now, but the golf course is getting tougher every day," said Singh.
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