Ratchanok Intanon and Pornpawee Chochuwong will battle it out for a place in the women's singles final while Dechapol Puavaranukroh and Sapsiree Taerattanachai also booked their berth in the mixed doubles last four of the US$350,000 (approximately 10.8 million baht) BWF Thailand Open.
There was two huge upsets on Friday as the top seeds of both men's and women's doubles categories were sent tumbling out of the BWF World Tour Super 500 event at Indoor Stadium Hua Mark.
Two-time champion Ratchanok had little trouble against her Chinese opponent Chen Xiaoxin on Friday, moving past the 23rd-ranked player 21-17, 21-15 in 45 minutes.
The Thai sixth seed set up a last-four clash with compatriot Pornpawee, who needed three games to overcome Cheung Ngan Yi of Hong Kong 21-15, 15-21, 21-12 earlier.
In the top half of the draw, top seed Chen Yufei will take on Sayaka Takahashi for a place in the final. China's world No.4 Chen eased past Soniia Cheah of Malaysia 21-15, 21-8, while Takahashi scraped past Fitriani Fitriani of Indonesia 22-20, 15-21, 21-14 in the other quarter-final.
Mixed doubles stars Dechapol and Sapsiree edged past He Jiting and Du Yue 20-22, 21-17, 21-14 in 82 gruelling minutes and will play another Chinese pair, Wang Yilyu and Huang Dongping in the semi-finals. The second seeds defeated Seo Seung-Jae and Chae Yu-Jung of South Korea 21-19, 21-14.
Third seeds Yuta Watanabe and Arisa Higashino of Japan will square off against Tang Chun Man and Tse Ying Suet of Hong Kong in the other semi.
In the men's singles event, seventh seed Kanta Tsuneyama of Japan downed Sai Praneeth B of India 21-18, 21-12. He will play either Angus Ng Ka Long or Thai star Khosit Phetpradab in the last four.
Lee Zii Jia, who overcame Shesar Hiren Rhustavito of Indonesia 11-21, 21-14, 21-13, will meet either sixth seed Kenta Nishimoto of Japan or third seed Chou Tien-chen of Taiwan in the other semi-final.
Men's doubles world No.1 pair Marcus Gideon and Kevin Sukamuljo, who won four titles so far this season, including last week's Japan Open, went down to fifth seeds Hiroyuki Endo and Yuta Watanabe of Japan 17-21, 21-19, 14-21.
The Japanese duo will go on to play Li Junhui and Liu Yuchen in the last four after third seeded Chinese beat Goh V Shem and Tan Wee Kiong of Malaysia 21-16, 21-19.
The other semi-final will be a battle between two unseeded teams, India's Satwiksairaj Rankireddy and Chiraq Shetty and South Korea's Ko Sung-Hyun and Shin Baek-Cheol.
Women's doubles quarter-finals also saw a surprise result as No.1 seeds Mayu Matsumoto and Wakana Nagahara were beaten on Friday.
The Japanese stars were stunned by eighth seeds Du Yue and Li Yinhui of China 18-21, 21-18, 15-21. They will play sixth seeds Lee So-Hee and Shin Seung-Chan of South Korea in the final four.
Seventh seeds Shiho Tanaka and Koharu Yonemoto of Japan will play unseeded Koreans Chang Ye-Na and Kim Hye-Rin in the other semi-final.