Just four minutes later, Indonesia doubled their advantage when Ricky Kambuaya charged into the opposition area before playing a neat backheel to find Witan Sulaeman, who expertly squeezed his shot into the bottom corner.
The contest was effectively over on the stroke of halftime when Marselino Ferdinan added a third, pouncing on a clearance on the edge of the box and lashing away a first-time effort that nestled into the back of the net via a ricochet off an opposition defender.
Myanmar were able to pull one back six minutes after the hour mark when Win Naing Tun - having had an earlier goal ruled out in the first half - found space down the right and cut inside an opponent before firing away a shot that skimmed off Alfeandra Dewangga and flew past a hapless Ernando Ari.
But it proved to be a mere consolation as Indonesia held on for a third win of the campaign to seal a top-two finish in Group A and a place in the last four.
It initially looked as though the bottom-placed Timorese might pull off a real upset as they held Vietnam at bay in the first half, but the breakthrough eventually arrived in the 53rd minute when Nguyen Van Tung escaped his marker's clutches to glance home a Le Van Xuan cross at the back post.
Van Xuan then emerged as a real creative force once more 12 minutes later, floating in a corner that Ho Thanh Minh did well to climb high and meet with a powerful header into the back of the net to secure the win.