Trailing most of the game, Arizona State (18-3, 7-2 Pac 12) rallied late in the second half, erasing a seven-point deficit with an 11-4 run that included a layup and four-straight free throws from Thomas and tied the game at 62 with 32 seconds left. Promise Amukamara then put the Sun Devils ahead for the first time since the opening period with a free throw, and Thomas padded it with a final free throw.
Deja Mann contributed 11 points, while Katie Hempen and Sophie Brunner had 10 each for Arizona State.
Oregon State (12-9, 4-5) led 41-33 lead at the break.
Deven Hunter led the Beavers with 13 points and nine rebounds, while Gabriella Hanson added 12 points and eight rebounds.