My company went to Da Nang for a few days. From HK it takes about two hour flight to Da Nang Airport, which is rather a short flight.
The immigration process is interesting. Only a few countries have visa free to Vietnam, i.e. most of us have to get a visa to enter. People may get visa from consulate in HK by paying HK$6xx for a single visit tourist visa, or getting a pre-approved visa before arrival.
We took the second route because it is cheaper overall. You have to first get a travel agent (mostly in vietnam) to obtain an approval letter. The cost of it is about US$8 per head. Then upon arrival, you have to pay US$25 per head to get the visa at the visa counter just before the immigration as shown on below picture. Hence the overall cost is about USD33 per head, i.e. HK$3xx.
The story is not ended here. The approval letter is a PDF file with a list of visitors on the attachment page and the list shows a number of visitors (who are unknown to you) with the name and passport information. That means you are holding the same approval letter with tens of different visitors and you know their nationality and passport number, no privacy at all.
Well, service level is related to the price. Some travel agents offer you some special service. The one I used has these:
a) pay US$8 more, you can have a private letter for your own group, i.e. the attachment page only shows your group of people
b) pay US$20 per head, you can have their staff to help you get the visa, so that you need not to line up. Their staff will help you get the visa at the counter
c) pay US$30 per head, you can have the service in b) PLUS a separate custom officer to check you passport, i.e. express immigration service so that you need not to line up at custom.
Isn't it amazing???
At last, we pay USD8 more to get a private letter.