[tankawen]

Source: Singapore Ministry of Foreign Affairs

While you should ensure that you have sufficient funds for
the duration of your stay in Vietnam and may be asked to show evidence of
financial sufficiency before you are allowed entry into the country, do not
carry too much cash. According to the State Bank of Vietnam (SBV),
foreigners are allowed to bring into/out of Vietnam of up to USD 5,000 or
equivalent. Specific paperwork and approval are required before you are
allowed to bring in currency beyond this amount into the country.


Means no need to declare if bringing below USD5k or equivalent