Thai stars Pornpawee Chochuwong and Supanida Katethong will face off in the quarter-finals of the US$420,000 BWF Kumamoto Masters Japan in Kumamoto on Friday.
Unseeded Pornpawee rallied to defeat fourth seed Han Yue of China 17-21, 21-12, 21-14 in 57 minutes, while seventh seed Supanida defeated Line Hojmark Kjaersfeldt of Denmark 21-15, 21-18.
The two are the only Thai singles players left in the tournament after both Kunlavut Vitidsarn and Ratchanok Intanon exited the Super 500 event in the last 16 stage on Thursday.
Third seed Kunlavut, who claimed his first title of the year at the Korea Masters on Sunday, suffered a shock defeat against Chi Yu-jen of Taiwan, losing 19-21, 10-21 in just 34 minutes.
Chi will face Li Shifeng of China or Kenta Nishimoto of Japan in the quarter-finals.
Earlier, Ratchanok fell to her Indonesian rival Gregoria Mariska Tunjung 14-21, 15-21. The fifth seed, who also knocked out Ratchanok in the Paris Olympics quarter-finals, will play Denmark's Mia Blichfeldt in the last eight.
Mixed doubles duo Dechapol Puavaranukroh and Supissara Paewsampran continued their campaign with a hard-fought victory on Thursday.
The Thai pair knocked out Dutch duo Robin Tabeling and Alexandra Boje 21-12, 17-21, 21-19 to set up a quarter-final clash with Malaysians Hoo Pang Ron and Cheng Su Yin, who also needed three games to overcome seventh seeds Rinov Rivaldy and Pitha Haningtyas Mentari of Indonesia 18-21, 24-22, 21-10.
Another mixed pair Ruttanapak Oupthong and Jhenicha Sudjaipraparat also progressed after beating Hiroki Nishi and Akari Sato of Japan 21-14, 21-18. They will face Thom Gicquel and Delphine Delrue of France in the quarter-finals.
Big upset
Meanwhile Canada's Michelle Li ousted India's Pusarla V Sindhu 17-21, 21-16, 21-17 and will next face South Korea's Sim Yu-Jin, who eliminated women's top seed Wang Zhiyi of China 26-24, 21-18 while second seed Akane Yamaguchi of Japan beat Lo Sin Yan of Hong Kong 21-12, 21-8.
In the men's singles event, top seed Viktor Axelsen of Denmark defeated Lei Lanxi of China 14-21, 21-14, 21-9; second seed Kodai Naraoka of Japan downed Toma Junior Popov of France 24-22, 21-9.