Choi enjoyed a near flawless round of golf, except for a costly blunder on the par-3 15th, in shooting a 4-under 67 that included five birdies.
The lead could've of been seven but Choi took a double bogey at the 15th, his only miscue of the day.
Already holding a two shot advantage heading into Saturday, Choi carded one of the day's lowest round, despite his double, as his nearest competitors couldn't muster a charge.
Rookie of the year candidate Pat Perez is Choi's closes pursuer at 9-under. An eagle three at the par-5 14th vaulted him into second place and got him to 11-under, but followed that up with a double bogey of his own, and will start five back of Perez on Sunday.
Glen Day and Donnie Hammond are in a tie for third, six strokes off the pace, posted a 1-under 70 and 2-under-par 69 respectively.
Teen phenom Ty Tryon, who shot himself into contention during the second round, could only manage a 1-over 72 that dropped him into a tie for 2oth. He was tied for 8th after round 2.
Rod Pampling, second going into the round, shot a 2-over 73 and is alone in fifth, seven behind Choi.
Forty-eight-year-old Peter Jacobson had four birdies and a lone bogey for a solid 4-under 67. He's one of a huge group of 14 that's tied for eighth at 4-under.
Full-field scores from Tampa Bay Classic