Can anyone recommend a travel agent in Bangkokwho can quickly obtan visas for Vietnam?

Gerald hits it right on. A thumbs up rating is deserved.

Getting a VN is no problem nowadays. The cumbersome bureaucracy of 10 years ago is gone.

If you don't have time, you can use a trusted colleague or a travel agent, e.g., there is one just down the stairs from the Ploenchit BTS station.

Using a travel agent will cost you a fee, but it will not make the process at the VN embassy go faster than if you went yourself.

It is therefore a question of cost vs. convenience, not speed.

I don't believe you need a travel agent, you can send anybody to the embassy with your documents who can apply and receive a visa for you. You can print out the application from the website, and along with the photos, the fee and your passport, you can designate anybody to represent you there. The visa normally takes 4-5 working days, but since you say you will be in Bangkok only 3 days, you will need to pay the extra fee for the expedited overnight service. I've received two Vietnam visas this year that I applied for myself and I probably didn't spend more than a total of 10 minutes at the embassy for both visas, it's a very simple procedure, if you have the time to get to the embassy, it doesn't take long, you do need to return or have someone return the next day to pick it up. The embasy is located on Wireless Rd., just down from the American Embassy near Sukhumvit Rd., the website explains the process:

http://www.vietnamembassy.or.th/visa.html