visa to HK for a group of Vietnamese

If you go there for leisure or relax purpose, you should apply for a visit entry permit. You should first prepare the required documents:
1. The application form and a passport-sized color photo taken recently
2. Copy of your passport
3. Transportation arrangement such as flight itinerary
4. Proof of financial support
5. Travel plan to HK
And then submit your application to the embassy of Vietnam to apply for it.