The match was controlled by the Koreans right from the first whistle and they got into an early lead through Lee Seung-woo's shot inside the Vietname's penalty box in the 7th minute of the match.
The reigning Asian Games champions continued their assault on Vietnam's defence and quickly doubled their lead two minutes before the half hour mark. This time, Hwang Ui-jo reacting quickest to Son's pass.
Such was Korea's control on the first half, that Vietnam did not get a shot at goal to trouble one of Korea's 2018 World Cup stars in goalkeeper Jo Hyeon-woo.
It was a similar affair in the second half with Korea continuing to press on their advantage and it only took Lee another 10 minutes after the restart to claim his second goal in the match.
Even though they trailed by three clear goals, Vietnam showed some fighting spirit to at least reduce the deficit when Tran Minh Vuong's free kick in the 72nd minute made it 3-1.
Vietnam tried to find the next goal but it just wouldn't come even though chances did fall to star men in Nguyen Cong Phuong and Nguyen Van Quyet. Korea closed out the game and will await the victors between Japan and United Arab Emirates.