After two matches, Vietnam and Thailand have six points each, while Malaysia have three, with each having two more matches in hand.
Vietnam will qualify if they beat Malaysia. If it is a draw, Vietnam will need to avoid defeat against Thailand in their last match to qualify.
If Vietnam draw with Malaysia and lose to Thailand in the last game, it will come down to Malaysia's match against Singapore. Vietnam have a better goal difference (+4) than Malaysia (+2), but if the latter beat Singapore by a margin of more than two goals, Vietnam will be eliminated.
If Vietnam lose to Malaysia, they will have to beat Thailand and wait for other results, and goal difference will take center stage.