Hi there, Joy.
For now, you can only assign one currency per customer. You might want to create different customer profiles for each currency. Then, create an invoice on that profile based on the currency that you will be using.
Just make sure to label each profile or add a unique character since you can't use the exact same name twice. For example, add USD, Euro, or Dirham at the end of their names so it's also easier to select which one to use when creating an invoice.
We have more details about this feature in this Help article: About Multicurrency
In addition, let's send a feature request about assigning multiple currency on a single customer. You can send it through the Gear icon and click Feedback.
Feel free to reply to this thread if you need anything else.. We're always here to help.
