score:6
From US Department of State (here): "In Singapore, you may be taken in for questioning if you donβt have your passport with you."
There is also a section titles "Surrendering your Passport" that addresses surrendering your passport to police officers, hotels, or employers as a guarantee. It is common for domestic helpers to surrender their passports in Singapore.
If you are required to have you passport on you at all times it is usually explicitly stated. The US DoS page for Malaysia states, "You should carry your U.S. passport and current social visit pass (visa) with you at all times..."
The US DoS page for Thailand states: "We strongly recommend that U.S. citizens carry proper travel documentation at all times. Thai police occasionally stop travelers in popular tourist areas to check their passports. Please carry at a minimum a copy of your U.S. passport identification page and current Thai visa to avoid detention by the Thai immigration police."
Upvote:4
Singapore does not require residents to carry their NRIC with them (National Registration Identification Card), so one can reasonably assume that having your passport on you at all times is also not required. But that said, having at least a copy with you is always advisable.
In other SE Asian countries where residents are required to have their IDs with them (such as Thailand), then travelers are bound by the same rules and the only legal ID for a tourist is their passport.