At present, there is no information about the Embassy of Vietnam in Cook Islands.
If you are holding a Cook Islands passport, you may visit the nearest Vietnam Embassy in the neighboring country to apply for a visa to Vietnam by yourself.
If you are citizen of other countries currently living in Cook Islands, you can apply Vietnam visa online through this form:
It takes 01 business days to get an approval letter via email. Once you have the visa approval letter, you can get a visa at airport when you arrive in Vietnam.
Embassy of Vietnam in other countries