Friends in Vientiane strongly recommended the train, which we're doing next month. They said that booking isnt as crazy as it used to be, and that hotels can easily book tickets for you when reservations become open at 3 days out. Alternatively, you can use a booking service. Security also has gotten laxer than when it first opened, they said, and various threads on other sites seem to agree. Didn't specifically get any info on baggage, but we'll be traveling with large suitcases and I can report back if youre able to wait til early March!

We looked at flights, but they are fairly infrequent, and have been highly discouraged from driving.