LA Manager Joe Torre will make his 14th straight playoff appearance.
Thome, acquired from the White Sox Aug. 31, hit the big single while batting for winner George Sherrill (1-0) with one out in the top of the eighth.
Ronnie Belliard had three hits, including a solo homer.
Manny Ramirez and Mark Loretta had two hits and one RBI apiece, while three others had one RBI for the Dodgers, who clinched a post-season berth for the third time in four years.
They reduced their magic number to three for clinching the National League West Division.
Pittsburgh got a two-run single from Andrew McCutchen.
Andy LaRoche hit a solo homer, while Luis Cruz had two hits and one RBI for the Pirates, who have lost 24 of 28.
The losing pitcher was Denny Bautista (1-1).
Copyright 2009 by United Press International.