South Korea, who are 30 places below Vietnam in the world ranking, surprised Vietnam when Shin Jong Hoon sank an early goal in the first minute of play.
Vietnam equalized just a minute later thanks to a finish by Nguyen Minh Tri that rebounded from Shin’s leg and went straight to the back of South Korea’s net.
Vietnam then pulled ahead in the 16th minute with a second goal.
The Vietnamese netted a third goal in the 17th minute when Minh Tri won the ball and started a counter-attack with Pham Duc Hoa, who took it inside the box and finished in the net to make it 3-1 for Vietnam.
In the second half, South Korea increased its intensity by having goalkeeper Seo Jung Woo on the attack.
Vietnam were under great pressure but the excellence of keeper Ho Van Y helped maintain their lead.
Pressure was taken off Vietnam’s shoulders when Tran Thai Huy scored the fourth goal in the 34th minute, putting an end to South Korea’s hope of making a comeback.
He fainted past Park Jeong Jin and ran down to face keeper Seo before finishing from a tight angle.
Vietnam scored a fifth goal one minute later when Duc Hoa chipped the ball over the keeper.
The 5-1 win against South Korea put Vietnam on top of Group D.
Saudi Arabia defeated Japan 2-1 in the other Group D match.
The 2022 Futsal Asian Cup is taking place in Kuwait from Tuesday, September 27 to October 8 with the participation of 16 teams divided into four groups.
The top two teams from each group will advance to the quarterfinals.
Vietnam will play Saudi Arabia on Friday and Japan two days later.