PLANE:
I recently flew business class from Hà Nội to Đã Nẵng.
Almost every travel website wanted around $400 USD or more for the one-way flight.
By booking directly through VietnamAirlinesDOTcom (NOT .ORG) my ticket cost ₫3,200,000 (about $137 USD) about a week ahead of travel.
TRAIN:
I'm heading to Huế from Đã Nẵng today via the train for 4 days of exploring.
Just to learn how it's done here, I decided to purchase my tickets in advance at the Đã Nẵng station.
I'm VERY glad I did.
In searching for ticketing information, I found that the actual website for the national railways is not very user friendly for an English-only viewer.
However, a website, Vietnam-RailwayDOTcom, was always first in my Google results, after promoted sites.
It proved to be a great source of planning information but a horrible rip-off.
The website quotes a price of $25 USD for a soft berth on my selected train.
At the station, I was charged ₫152,000 (about $6.50 USD).
I needed my passport to make the purchase in person.
Make sure you take a number first.
Electronic signs will indicate which agent will help you.
Also, have all of your information--date, time, train number, departure city, arrival city and class of ticket--prepared to show the ticketing agent (maybe type it into a smartphone note app and show it to them).
NOTE: Google Translate does NOT do a good job with "soft berth" or "soft bench".
Instead, if you want that class, write the English "Low (or High, if you want), Room4 beds, Air-con" which is what prints out on the boarding pass.
In Đã Nẵng, the ticketing office is in the low-slung building to the left as you are facing the main station building.
If you have special info regarding other cities or routes, please share.