You can’t get into the country without a visa. It is very important that you get a visa for Vietnam before crossing the border. I got mine in Bangkok, but you can easily obtain a visa from any Vietnamese Consulate around the world. The cost is 2,000 Baht from the Consulate in Bangkok, check the visa cost in your home country.
There’s an online form to fill out and print. Make sure you have a passport sized photograph to attach to it.
The Consulate is located near Phloen Chit BTS.
Walk down Wireless Road and there is an inconspicuous door with a simple sign saying “VISA Hours : 9:00-12:00; 14:00-16:00”.
Enter the office and wait in line. During the application drop- off hours, the office is fairly empty. There is a counter for submitting your application and a separate one for the cashier. They will inform you on which day you can come back to pick up your passport.
The passport pickup hours are from 16:00-17:00 each day. Thai public holidays and Vietnamese public holidays are observed, so make sure you turn up on a day when the office is open.
Typically, your visa will be prepared in four days or less.
I wasn’t offered the option of an express application process – however, I believe you could ask for it explicitly if you required. Of course, you should expect to pay a higher fee – usually 20-30% higher than the standard application fee. But depending on how much time you have, you may need to go for the express option to ensure you get the visa and passport back in time.