Host Myanmar beat Vietnam 2-1 in the final match of Asean U-18 Championship Group B on September 13 and advanced into the semi-final.
Myanmar fielded its strongest squad, including winger Pyae Sone Naing, who are returned from injury.
Myanmar were losing before the interval after Vietnam scored an early goal. Striker Win Naing Tun was being squeezed off the ball by two Vietnamese defenders but a 73rd-minute free kick just outside the penalty area was slotted home by midfielder Myat Kaung Khant. Substitute Lwin Moe Aung scored the winning goal from a close range in the 86th minute.
Indonesia thrashed Brunei 8-0 to win Group B, followed by Myanmar. Indonesia will meet Thailand and Myanmar will play Malaysia in the semi-finals on September 15.