| They are all excellent choices... Vietnam has some fascinating sights, form Halong Bay to Hue and all the war relics. Nice beaches, good food, good accommodation and dirt cheap but you need to get a visa. Language can be a bit more of an issue and some areas have more beggars.
Bali will be more touristy but easy to get away from Kuta beach and see nice black volcanic sand beaches, temples, snorkeling. Also very nice food and lots of cheap accommodation. Visa on arrival...People are generally nice but can be a little annoying
Thailand is the easiest place to visit with good tourist infrastructure, good food, nice people, few areas where you get hassled. Big country so you'd have to focus on one area depending on whether you want beach, adventure, nightlife etc... Phuket, Krabi, Koh Samui and the Chiang Miai area would be excellent choices. Avoid Pattaya unless you're into sleaze...Visa on arrival | 
