Khin Maung Lwin had given Myanmar the lead in the 13th minute of a drab first half in which neither team shone but a half-time reshuffle by Lions coach Raddy Avramovic swung the balance back in favour of his side in the second 45 minutes.
Aleksandar Duric levelled the score when he tapped in from close range just after the hour. And Agu Casmir scored three minutes into stoppage time to secure the win which put the Lions within touching distance of the semi-finals and sent Myanmar crashing out.
It was little more than the three-time winners deserved after a double change at half-time saw Casmir replace the ineffective Noh Alam Shah while Muhammad Ridhuan made way for Khairul Amri.
Amri’s pace down the left flank, in particular, gave Singapore a significant boost, lifting the tempo of a team that had looked flat and devoid of inspiration in the opening 45 minutes.
It was during the first half that Myanmar put their heavy opening game defeat at the hands of Vietnam behind them as Khin Maung opened the scoring.
With just 13 minutes on the clock, the midfielder finished off a fine move that saw the Singapore defence sliced open before Khin Maung scored with a well taken right footed effort.
Singapore rarely threatened, at least until six minutes before the break when defender Baihakki Khaizan somehow managed to put the ball over the bar after Jumaat Jantan’s corner found him with time and space to pick his spot.
Avramovic saw enough in the first half to ring the required changes at the interval and the Singapore team that came out for the second half was a different proposition to the tame beast that finished the first.
Casmir should have equalised in the 50th minute when Jumaat’s cutback found him in a position to capitalise, only for the striker to push his effort wide of goal.
Less than a minute later, Duric raced through the Myanmar defence before smashing a right foot shot beyond goalkeeper Thiha Si Thu and high into the corner. However, he had already been flagged for offside.
But Singapore were level 10 minutes later when Casmir received the ball from Mohammad Shahril before beating Yan Aung Win and slotting the ball beyond the goalkeeper. From there, Duric was left to roll his effort home.
Despite being in the ascendancy, Singapore still struggled to break down Myanmar’s resistance. It nearly got worse in the 69th minute when Yan Paing had the Islanders’ hearts in their mouths as his right foot shot from 10 metres out crashed against the crossbar.
But with seconds remaining, Casmir drove the ball home after a lay-off from Duric to end any resistance from Myanmar and improve his side’s chances of progressing to the semi-finals.