International Master (IM) Pham Le Thao Nguyen grabbed her fourth win in a row to stand No 1.
Nguyen, No 7 seed, defeated No 1 seed Lei Tingjie of China. She will meet with her teammate Vo Thi Kim Phung in the next round.
Women’s IM Phung beat IM Munguntuul Batkhuyag of Mongolia to have 3.5 points and place second in the ranking.
Women’s Grandmaster Nguyen Thi Mai Hung won over country-fellow WGM Nguyen Thị Thanh An. She has three points and is at third.
Hung is set to play Lei on May 16.
On the men’s side, Vietnamese players were not as successful.
No 10 seed Nguyen Ngoc Truong Son has 2.5 points and is down to No 23 after the fourth match.
His four teammates including Asian U20 champion Tran Tuan Minh are out of top 30.