After losing the opening game due to uncharacteristic errors, Ratchanok raised her level to take the second game to level the tie. Thanks to a barrage of unforced errors from her opponent.
In the topsy-turvy final game, Ratchanok needed up to four match points before she could knock out the world No 1 in the end, generating two great shots to wrap up the encounter that last more than hour.
She will take on Akane Yamaguchi of Japan on Saturday in the semi-finals.