Supanida Katethong and Kantaphon Wangcharoen advanced to the last 16 of the US$850,000 BWF Japan Open in Yokohama on Wednesday.
In her first tournament after the Paris Olympics, Supanida was forced to dig deep before she defeated Sung Shuo-yun of Taiwan 12-21, 21-14, 21-13 in the women's singles event.
Supanida will play Ester Nurumi Tri Wardoyo of Indonesia for a place in the quarter-finals after the Indonesian defeated another Thai hope Pornpicha Choeikeewong 21-14, 21-17 earlier in the day.
Kantaphon Wangcharoen had an easier opening match than his fellow Thai, getting past Brian Yang of Canada 21-8, 21-19 in 42 minutes at the World Tour Super 750 event at Yokohama Arena.
Kantaphon will face India's Sathish Kumar Karunakaran, who progressed after third seed Anders Antonsen of Denmark pulled out of their first round match with an injury.
Mixed doubles pair Supak Jomkoh and Supissara Paewsampran also advanced to the last 16 as they knocked out fourth seeds Kim Won-Ho and Jeong Na-Eun of South Korea 21-18, 21-14. Supak and Supissara will next play Jesper Toft and Amalie Magelund of Denmark.
Pornpawee Chochuwong exited the tournament after losing to second seed Akane Yamaguchi of Japan 14-21, 18-21.
Supak and Kittinupong Kedren also lost their men's doubles opener, going down to Korean third seeds Kang Min-Hyuk and Seo Seung-Jae 15-21, 21-16, 16-21.
Another women's singles hope Busanan Ongbamrungphan won her opening match on Tuesday against Zhang Wen-Yu of Canada 21-15, 21-13.
She will play third seed Wang Zhiyi of China in the last 16.
In other notable results on Wednesday, women's fifth seed Han Yue of China defeated Tomoka Miyazaki of Japan 21-15, 22-20 while men's eighth seed Kodai Naraoka of Japan downed Lee Chuek Yiu of Hong Kong 18-21, 21-9, 21-19.