The 2-2 draw against arch rivals Thailand after conceding a bizarre first goal and missing a penalty ensured Vietnam finished on top of Group B.
Vietnam lost the first goal in the 5th minute as keeper Nguyen Van Toan distrubuted to the ball right into Thai striker Supachai Jaded.
Six minutes later, Toan did not pick his spot well and let Suphanat Mueanta put the ball into an empty net.
Vietnam players did not let fans down for long. They narrowed the gap in the 15h minute after Tien Linh broke through three defenders in the box to headed the ball in from a cross in the left wing.
The second half saw many attacks from Vietnam, but they failed to score another goal, until a penalty opportunity, which turned out to be even more dramatic than the beginning of the game seemed.
Tan Sinh's penalty was denied by Thailand keeper Muangnam, and Duc Chinh could shove in the rebound.
However, Vietnam were allowed to take the penalty again as the referee ruled that Muangnam had moved in front of the line before Tan Sinh touched the ball.
Tien Linh made no mistake with the second chance, scoring the equalizer for Vietnam who managed to maintain the draw until the final whistle.
The hard-fought draw earned Vietnam another point and kept them at top of group B, with Indonesia second.
Vietnam will play Cambodia in the semifinal at 7 p.m. on Saturday (Hanoi time) and Indonesia play group A winner Myanmar.