The Singapore dollar uses ISO code SGD, often written S$ to distinguish it from other dollar currencies. A bare dollar sign on an international site is therefore insufficient. Check the account currency explicitly, then read the same code on deposit and withdrawal instructions. [1]
Singapore dollar
Currency settings
If the account is maintained in SGD, its balance can be compared directly with the Singapore-dollar amount sent from a local account. If another currency is involved, record the conversion and any separate charge. The presence of a Singapore-facing payment option does not establish that the betting balance itself is denominated in SGD.