Benyapa Aimsaard and Nuntakarn Aimsaard moved into the women's doubles semi-finals of the US$420,000 Hong Kong Open in Kowloon on Friday.
The fifth seeded Thai pair stunned top seeds Mayu Matsumoto and Wakana Nagahara of Japan 17-21, 25-23, 21-14 in the last eight of the World Tour Super 500 event.
"We have beaten the top seeds and it's our first win against them but we don't want to be satisfied. We want to be better tomorrow," said Benyapa.
They will next play sixth seeds Tan Pearly and Thinaah Muralitharan after the Malaysians defeated another Thai pair Jongkolphan Kititharakul and Rawinda Prajongjai 15-21, 21-14, 21-19.
Aimsaard sisters are chasing their second World Tour title of the year and fifth overall.
They won the Thailand Masters in February and were runners-up at the Thailand Open in June.
In the bottom half of the draw, seventh seeds Apriyani Rahayu and Siti Fadia Silva Ramadhanti of Indonesia defeated Li Wenmei and Liu Xuanxuan of China 21-15, 21-13.
They will play Maiken Fruergaard and Sara Thygysen in the semi-finals. The Danish duo defeated Rena Miyaura and Ayako Sakuramoto of Japan 21-19, 21-18.
In the women's singles quarter-finals, top seed Akane Yamaguchi of Japan defeated Zhang Beiwen of the United States 21-13, 21-15, but third seed Carolina Marin of Spain exited the tournament after losing to fifth seed Gregoria Mariska Tunjung of Indonesia 9-21, 18-21.