Singapore is the clearing center for credit card transactions. The best method of payment should be prepayment. If that is not a possibility bring cash Although the credit card processing may work it can't be counted on. Good news travels is a reputable travel agency there or others outside the country can assist.
Definitely bring cash as commerce is flourishing in Scott market and local markets even without ATMs.
It's also a place to bring non controversial items such as classic books school supplies or shoes clothes that can be left for the many that do not have access to basic items