The only goal of the game was scored in the 65th minute by defender Nguyen Thanh Hien.
Vietnamese striker Cong Phuong failed to dribble the ball past several rivals and the loose ball came to Hien on the left wing, who blasted a long shot from a distance of around 20 meters to score the opening goal.
The Vietnamese side had better ball possession and controlled the rhythm of the match but they had trouble getting past the thick defensive wall of Laos.
This is the third win for Vietnam in Group B after they crushed Brunei 6-0 on May 29 and Malaysia 5-1 on June 2.
Vietnam will next take on Timor Leste on June 7 and Thailand on June 10.
Group B includes Timor-Leste, Laos, Malaysia, Thailand, Brunei, and Vietnam. The other regional teams including hosts Singapore, Indonesia, Myanmar, Cambodia, and the Philippines are in Group A.
The 28th Southeast Asian Games will open in Singapore on Friday, June 5, and close on June 16.
What the stars mean:
★ Poor ★ ★ Promising ★★★ Good ★★★★ Very good ★★★★★ Exceptional