Top seed Son Wan Ho suffered a surprise third-round defeat at the Korea Masters on Thursday.
World No 2 Son was sensationally beaten 21-12, 21-12 by unseeded countryman Kim Min Ki in a match that lasted just 32 minutes.
The big win earns Kim a quarter-final match-up with Taipei’s Lee Chia Hao.
There were no further surprises in the men’s draw, with seeds Jeon Hyeok Jin, Brice Leverdez and Khosit Phetpradab all advancing safely.
Seventh seed Phetpradab reached the quarters with a 21-17, 21-10 victory over ninth seed Chong Wei Feng.
In the women’s draw, top seed Sung Ji Hyun kept Korean hopes alive with a hard-fought 14-21, 21-13, 25-23 victory over Wang Zhiyi.
Second seed Natchaon Jindapol also advanced, as did Lee Jang Mi and Pornpawee Chochuwong.