The game was held at the Shahid Dastgerdi Stadium in Iran's capital Tehran due to the conflict in Syria, but the nominated hosts were in impressive form to boost their chances of reaching the 2015 finals in Australia.
Sanharib Malki gave Syria the lead 10 minutes in, sweeping home after a strong run down the right and cut-back from Ahmad Al Doni.
Syria peppered the Singapore goal, but found Hassan Sunny in impressive form as he routinely denied them.
However, his goal was finally breached again seven minutes from time as Al Doni netted a strike of his own, powering the ball in after a looping cross from the left.
An error from Sunny gifted Syria a third as he fumbled Oday Jafal's weak header into the net.
And the scoreline was rounded off by Abdul Fattah Al Agha's bullet header in the third minute of stoppage time.
Syria move up to third in Group A and will be targeting strong results against Jordan and Oman in their remaining fixtures as they bid to reach the showpiece event.
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