Vennala took the opening game 21-18 with some sharp rallies but Janyaporn fought back to edge the second 21-17, forcing the match into a decider.
In the final game, Vennala pulled ahead in the closing stages, eventually sealing a 21-18, 17-21, 21-17 victory to earn her semi-final berth.
Both Indians now face opponents from the People’s Republic of China in the semi-finals, with Tanvi set to take on eighth seed Yin Yi Qing and Vennala going up against Liu Si Ya.
Tanvi and Vennala are the only Indian challenges still left at the ongoing continental showpiece with none of the men’s singles players or doubles pairings managing to make it past the pre-quarterfinals.
This is the first time India have two women’s singles players making it through to the semi-finals at the continental meet.