Friend's bachelor's to Vietnam in December?

In December, the north of Vietnam is the best place for the time. It's the winter time in Vietnam, you can visit Sa Pa. From Hanoi, you can catch night train to travel to Sapa which will save than night bus. You can homestay at local people in Tả Phìn village

In December, you can visit Ho Chi Minh City city and some nearby floating markets in Mekong delta.

In December, it is often cold in Hanoi and especially in North-western region such as Sa Pa. Snow occasionally comes and leaves but it might get colder than one expect. Prepare warm clothes or you might be trapped in an undesirable flu. Also bring a lot of lip balms and hand-cream, for the dry weather may make you suffer intensely. As you move southward, it is not as dry and cold. There are pleasant breezes and the sun is on until late afternoon.