In QuickBooks Online, you will be able to issue an invoice in a different foreign currency. However, when receiving payments, you can only use the home currency that matches the invoice.
For your situation, you can record the payment as you normally do. Then, add the information in the memo field. Here's an article for the steps: Record invoice payments in QuickBooks Online.
As an additional reference, you may open a virtual USD and/or SGD bank account at Wise to deal with multi currency transactions. Utilize the bank feeds if required.