Singh finished two strokes ahead of Charles Howell III and five clear of David Toms. The native of Fiji claimed his 11th career win on the PGA Tour.
Luke Donald, who won the rain-shortened Southern Farm Bureau Classic, jumped 67 places up to No. 96 in the rankings. In all, Donald has climbed a remarkable 426 places during the 2002 season.
The two tournaments were the final official events on the PGA Tour this season.
Tiger Woods remained atop the rankings. The No. 1 player in the world finished tied for seventh at the Tour Championship. Woods was followed by Phil Mickelson, Ernie Els and Retief Goosen.
Toms and Sergio Garcia exchanged places at fifth and sixth while Singh hopped over Padraig Harrington. Harrington, who trails Goosen in the race for the Order of Merit title, dropped to eighth. The two will battle for that title at this week's Volvo Masters Andalucia.
Davis Love III and Jim Furyk remained in the same positions from last week to round out the top 10.
Nick Price and Chris DiMarco stayed in spots 11 and 12. Angel Cabrera and Colin Montgomerie exchanged positions for the second straight week, with Cabrera now 13th in the rankings. David Duval, who did not play this week, still stands at No. 15.
Justin Leonard and Bob Estes each climbed one spot to Nos. 16 and 17. Michael Campbell fell two spaces to 18th followed by Robert Allenby. Scott Hoch moved up two spots to 20th in the rankings. Eduardo Romero, who was 20th last week, dropped down to No. 22 in this week's rankings.
Ian Poulter won the rain-shortened Italian Open on the European Tour and vaulted up 32 places to No. 80 in the world.