Women's doubles pair Jongkolphan Kititharakul and Rawinda Prajongjai lost to Nami Matsuyama and Chiharu Shida of Japan 15-21, 10-21 in their Group B opener at the US$2.5 million BWF World Tour Finals in Hangzhou, China, on Wednesday.
Also in Group B, South Korea's Baek Ha-Na and Lee So-Hee beat compatriots Kim So-Yeong and Kong Hee-Yong 21-11, 22-20.
The Thai pair will need to beat Baek and Lee on Thursday to keep alive their hopes of making it to the semi-finals.
Mixed doubles stars Dechapol Puavaranukroh and Sapsiree Taerattanchai and men's singles world champion Kunlavut Vitidsarn were due in action later Wednesday night.
Meanwhile, women's singles world champion An Se-Young also lost her first Group A match against Korean compatriot Kim Ga-Eun 18-21, 18-21.
Also in Group A, Taiwan's Tai Tzu-ying, champion in 2020, looked in good touch against the in-form Gregoria Mariska Tunjung of Indonesia, wrapping up her opening match 21-18 21-17.
In the men's singles, Anthony Ginting of Indonesia rallied to beat Kodai Naraoka of Japan 10-21, 21-10, 21-18 in Group A.
Men's doubles pair Kim Astrup and Anders Skaarup Rasmussen of Denmark avenged their defeat against Kang Min-Hyuk and Seo Seung-Jae at the world championships, beating the Koreans 21-10, 15-21, 24-22 in Group B opener.
In Group A, Takuro Hoki and Yugo Kobayashi of Japan won their sixth match in a row against Aaron Chia and Soh Wooi Yik of Malaysia in a battle between former world champions. The Japanese prevailed in three games 21-16, 14-21, 21-18.
Women's doubles defending champions Chen Qingchen and Jia Yifan of China had their hands full against younger compatriots Liu Sheng Shu and Tan Ning, before winning 21-14 21-17.