The notorious course is one of the very toughest to host The Open, all the more so when the wind blows in off the North Sea.
The Northern Irish star looks to win his second British Open title.
Swedish superstar Annika Sorenstam became the first woman in 58 years to appear in a PGA event when she played the Colonial in 2003.
The American's last victory in The Open came in 2006.
The 24-year-old, however, has not won since his Open success last July.
The South Korean-born American finished with a 27-under total of 257, one stroke better than the previous tournament record set by Steve Stricker in 2010.
The triumph helped Thidapa earn one of five places on offer this week in the Women's British Open.
The South Korean won with a stunning 31-under par total to smash the LPGA 72-hole scoring record.
Kelly Kraft was second on 266 with Jason Kokrak and Brandt Snedeker sharing third on 267.
Scotsman Knox defeated New Zealander Ryan Fox in the play-off.
Varner's bogey-free round left him alongside fellow American Kraft on 14-under 196 for 54 holes.
India's Lahiri had set an early target with a nine-under-par 61.
The 31-year-old world number 99 stood level with Simpson, the 2012 US Open champion, on 12-under 128 after 36 holes.
South Korean Kim Whee was one shot behind in second while Chilean 19-year-old Joaquin Niemann was on seven-under 63.
The 35-year-old from Turin became the first Italian to win a US PGA event since the late Toney Penna took the 1947 Atlanta Open.