Hi Mike 10.

You have me to help you record a payment from a differne tcurrency.

First, we'll have to create a dummy account in the home currency top track the movement between your home currency and the other foreign one.

1. From the Accounting tab, select Chart of Accounts.
2. Click New.
3. Under Account Type column, select Cash and cash equivalent.
4. On the Detail Type field, select Cash on hand.
5. You can enter Dummy Bank as its Name.

Afterwards, record the payment of the foreign invoice.

1. Select Receive Payment on the + New button.
2. Select the dummy account we created earlier on the Deposit To field.
3. Before saving, take note of the home currency amount displayed at the bottom right.

Then, we'll have to transfer the amount from the dummy bank account to the foreign account.

1. On the Transfer page, select the dummy bank account on the Transfer Funds From filed.
2. Select the bank of the foreign currency on the Transfer To box.
3. Under Currency column, select SGD.
4. Enter the amount that you take note earlier on Transfer amount.
5. Click Save and close.

I've also added this reference when you're ready to categorise the transactions:  Categorise and match online bank transactions. 

Keep me posted whenever you need help. I'll be around to help you out. Keep safe!