Ratchanok Intanon knocked out top-ranked Tai Tzu-ying to book her berth in the semi-finals of the US$700,000 (approximately 23.1 million baht) China Open in Fuzhou yesterday.
It was the Thai badminton star only second win in five meetings against the Taiwanese this year.
The world No.6 rallied from a game down to win their women's singles quarter-final clash 10-21, 21-9, 22-20 at Haixia Olympic Sports Center.
Ratchanok meets another old rival Akane Yamaguchi in today's semi-finals of the BWF Supeseries tournament. The Japanese fifth seed defeated China's Ji Shuthing 21-11, 21-19 yesterday.
Earlier, fourth seed Caroline Marin of Spain became the first player to make it to the last four after beating home hope He Bingjiao in a three-game thriller.
The reigning Olympic champion showed nerves of steel as she battled past the Chinese seventh seed 21-15, 22-24, 22-20 in a gruelling 92-minute encounter.
Marin takes on another Chinese Gao Fangjie, who defeated PV Sindhu in one of the day's biggest upsets. Gao stunned the No.2 seed from India 21-11, 21-10 in just 37 minutes.
In another surprise result, seventh seed Lee Chong Wei of Malaysia crashed out of the men's singles event.
The former world No.1 fell to Angus Ng Ka Long of Hong Kong 21-12, 15-21, 21-19.
Top-ranked Viktor Axelsen of Denmark had no such trouble in a 21-17, 21-14 win over Taiwan's Chou Tien-chen.
Meanwhile, Kunlavut Vitidsarn booked his berth in the semi-finals of the men's singles U19 event at the Korea Junior Badminton Championships yesterday.
The top-seeded Thai defeated Jia Wei Joel Koh of Singapore 21-17, 21-10 at Miryang City Badminton Stadium.
The 16-year-old rising star became the first male shuttler from the Kingdom to win the world junior title in Indonesia last month.
Second seed Ruttanapak Tubthong also made the semi-finals after an easy 21-15, 21-15 win over No.11 Guo Xinwa of China.
In the girls U15, second seed Thamonwan Nithiittikrai made it to last four after defeating Korean Kim Na-Yeon 24-22, 17-21, 21-16.