Exchange rate risk
In short
Exchange rate risk is the chance that the value of your USD income changes when converted to rupiah, because the IDR/USD rate moves between the day you are paid and the day you convert it.
If you are paid in USD but spend in rupiah, your effective income in IDR rises and falls with the exchange rate even if your USD rate never changes. Some freelancers convert and withdraw as soon as they are paid to lock in a rate; others hold USD in a multi-currency account and convert gradually. Neither is universally correct — it depends on your risk tolerance and how predictable your rupiah expenses are.