The main thing to consider is the weather, as it can be freezing cold
in the Northern mountains, and at the same time incredibly hot and
humid on the Central Coast. If you are traveling in the North or the
Central Highlands during the winter months definitely bring jeans and a
warm coat or sweater. It seems that it is always raining somewhere in
Vietnam, so lightweight rain gear is essential.
In the hot months, dress cool but conservative. Many Vietnamese cannot
understand why foreigners insist on wearing shorts, tank tops and
sleeveless t-shirts when they have the money to dress well. For the
Vietnamese, appearance is very important, so if you are dealing with or
as an official of any rank, make sure you are dressed appropriately.