Head coach Mai Duc Chung made three changes to the team that had beaten Cambodia 10-0 on Friday.
Against Indonesia, it took Vietnam just 39 seconds to open the scoring. Nguyen Thi Bich Thuy received a pass from the flank and took two shots to put the ball in.
Indonesia have never been a force in women’s football, and Chung’s players easily dominated the game. In the first half they scored five goals with key striker Huynh Nhu getting a hattrick and Pham Hai Yen adding a fifth.
Vietnam slowed down the tempo in the second half. Between the 61st and 63rd minutes Nguyen Thi Tuyet Dung scored twice to seal the 7-0 win.
While Vietnam are through to the last four, their last match against Myanmar will decide first place. Myanmar have also beaten Cambodia and Indonesia but have a goal difference of 16 to Vietnam’s 17.
Vietnam only need a draw in the match on August 20 to finish top.
They have set sights on winning the tournament, which is being held in Chonbury, Thailand. They finished third at last year's event, which Thailand won by defeating U20 Australia 3-2 in the final.