Five of the goals were scored in the second half of the game at Wunna Theikdi Stadium in Naypyidaw.
Vietnam created a couple of chances in the first half but failed to convert them before South Korea dominated the game.
Defender Lee Jeonbin opened the scoring for South Korea in the 45thminute following a simple attack on the right flank.
The ball was crossed into the midfield area in front of the Vietnamese box before finding midfielder Kim Seungyu, who headed it back to Lee Jeonbin. The latter then rushed in to blast a shot.
Blocked by Vietnamese keeper Van Truong, the ball bounced into the body of Jeonbin and rolled into the net.
Ten minutes into the second half, South Korea doubled their advantage with a goal by midfielder Kim Gunhee.
Korean defender Park Jaewoo rose up on the right side and made a cross to Kim Gunhee near the box of Vietnam. He moved up a couple of steps before shooting to send the diving ball into the middle of the Vietnamese goal frame.
In the 60th minute, the Koreans repeated their ‘attacking screenplay’ leading to the second goal to net their third.
Midfielder Suh Myeongwon sped up on the right wing before making a cross for substitute striker Shim Jehyeok to dash in and take South Korea to a 3-0 lead by a header.
In the 66th minute, Shim Jehyeok raced from the middle of the field to face keeper Van Truong, who played foul with a tackle.
Being awarded a penalty, Hwang Heechan successfully converted it into the fourth goal for his side.
The score was lifted up to 5-0 in the 80th minute of the game after Park Seung-ho made a long shot from 20 meters to defeat goalie Van Truong.
In a last-gasp counterattack, Kim Gunhee was set up in a favorable position, dribbling the ball past many Vietnamese players, including keeper Van Truong, to seal a 6-0 victory for South Korea.
At the AFC U-19 Championship 2014 held from October 9 to 23, Vietnam are in Group C with Japan, China, and South Korea.
The Vietnamese will play Japan on Saturday and China two days later.
South Korea are the defending champions at this competition. They beat Iraq 4-1 in a penalty shootout after drawing with them 1-1 in 120 minutes in the finale of the 2012 championship in the United Arab Emirates.
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