Fifth seed Ratchanok, who is chasing the first Birmingham title after twice finishing runner-up, eased past Soniia Cheah of Malaysia 21-9, 21-11 in just 31 minutes at Arena Birmingham.
Ratchanok, who is gunning for her second title of 2020 after her Indonesia Masters victory in January, will play the winner of the match between Aya Ohiri of Japan and Kim Ga-Eun of South Korea.
Busanan Ongbamrungphan joined Ratchanok in the round of 16 after she defeated Mia Blichfeldt of Denmark 21-15, 14-21, 21-16.
She has a tough assignment in the second round in the shape of top seed and world No.1 Chen Yufei of China.
Another Thai hope Nitchaon Jindapol failed to progress, losing to South Korea’s Sung Ji-Hyun 23-21, 21-10.
Phittayaporn Chaiwan, the other Thai in the women’s singles event, lost to Line Hojmark Kjaersfeldt of Denmark 21-18, 19-21, 21-9.
Women’s defending champion Chen survived a scare, rallying after losing the first game to beat An Se-Young of South Korea 14-21, 21-14, 21-15 in 67 minutes.
World champion Pusarla V Sindhu also advanced.
The Indian sixth seed defeated Zhang Beiwen of the United States 21-14, 21-17.
In the men’s singles event, Jonatan Christie became the first seeded casualty with the Indonesian sixth seed going down to Lee Zii Jia of Malaysia 21-15, 21-13.
Thailand’s two men’s singles players Kantaphon Wangcharoen and Khosit Phetpradab both crashed out.
Triple world junior champion Kunlavut Vitidsarn was due to play five-time champion Lin Dan later yesterday.
There was no trouble for Dechapol Puavaranukroh and Sapsiree Taerattanachai after the third seeds beat Ronan Labar and Anne Tran of France 21-12, 21-11 in the mixed doubles opener.
They will play Lee Jhe-Huei and Hsu Ya-ching of Taiwan in the second round.