Sihag, ranked 63rd in the world, took down the top seeded Katethong 21-19, 21-18 in straight games in front of the latter’s home crowd.
The Indian shuttler didn’t have best of starts to the match, trailing 0-5 and then 1-7 in the opening game. A slew of unforced errors from Katethong helped Sihag claw her way back to level at 9-9.
From there on, there was no looking back.
Though Katethong kept her in check for a major part of the match, Sihag managed to hold her nerves at crucial moments to wrap up a win in 40 minutes over the former world No 6.
Sihag will next face off against the fifth seeded Huang Yu Hsun of Chinese Taipei in the semi-finals.
Tharun, Isharani exit
Meanwhile, Tharun Mannepalli and Isharani Baruah crashed out of contention in men’s and women’s singles respectively.
Mannepalli went down 11-21, 17-21 in straight games to Zhu Xuan Chen of China in just 37 minutes, whereas Baruah was shown the door by Malaysia’s Wong Ling Ching.
Baruah lost 21-18, 16-21, 13-21 after being a game up in a contest which lasted an hour and four minutes.