This meant the Thai leapfrog ahead of S'pore to second in the group and only the top two teams qualify for the Asian Cup Finals in Qatar.
S'pore now have to win in Bangkok on Wednesday or face an exit from the ACQ as a draw may not be good enough.
Asian Cup Qualifiers - Group E
Singapore 1-3 Thailand
Singapore: Hassan Sunny, Noh Rahman (C), Baihakki Khaizan, Daniel Bennett, Shaiful Esah, Ridhuan Muhammad , John Wilkinson, Mustafic Fahrudin, Shahril Ishak(Indra Sahdan 72') , Noh Alam Shah (Khairul Amri 60'), Aleksandar Duric