Danh Trung took advantage of a misunderstanding between Hoang Anh Gia Lai’s Van Loi and midfielder Trung Nghia to strike into an empty net.
Captain Van Xuan was sent off at the 30th minute when he grasped Hoang Anh Gia Lai striker Hoang Tu in an attempt to prevent him from scoring.
The shortage of players, however, did not affect Vietnam’s power.
They continued to score in the 65th minute by Van Cong and 79th minute by Xuan Kien.
Hoang Anh Gia Lai also had to play with 10 men when in the 65th minute Trung Nghĩa was given his second yellow card.
Bao Toan netted the only goal for Hoang Anh Gia Lai about 20 minutes after the break.
In an early match, Chinese Taipei lost 0-2 to Myanmar.
With three wins, Vietnam top the ranking with nine points and will take a slot in the final. They will play second-placed Korean Gwangju FC on April 20 in the group’s last round match.
Hoang Anh Gia Lai, placed third, will take on Myanmar, who are fourth.
