The Lions have slipped to their third straight defeat, going down 0-1 to Hong Kong in an international friendly on Tuesday evening.
Bai He's 60th-minute tap-in from close range capped a convincing and feisty display from the hosts at the Mongkok Stadium in Kowloon.
Singapore goalkeeper Hassan Sunny pulled off three top-drawer saves to keep the scoreline respectable. However, missing key midfielders Shahril Ishak and Hariss Harun through injury, Bernd Stange's men failed to muster a meaningful shot on goal.
The Lions were thumped 1-6 by China in Tianjin last Friday. They next host Syria in an Asian Cup qualifier on Oct 15, having lost their opening two Group A matches.