This is where supporting documents become particularly important.
Outgoing international transfers are subject to Vietnamese foreign exchange regulations.
Foreigners with foreign currency in their accounts or legal income in foreign currency can transfer it abroad. When they have legal income in VND, they can also purchase foreign currency to transfer out of Vietnam in accordance with regulations.
The bank may request documents to justify the origin and destination of the money.
For example:
salary → contract + payment documents
sale of an asset → sales contract and corresponding documents
professional income → company documents and supporting evidence
savings initially transferred to Vietnam → proof of transfers
This explains an important rule:
Keep a documentary record of the origin of your funds in Vietnam.
A few years later, these documents can significantly simplify an international transfer.