Four airlines serve the city-pairs: Thai Airways, Lao Airlines, Lao Central Airline and Bangkok Airways

Bangkok Airways intensifies race on Vientiane route - http://tinyurl.com/axvjcvm

Normal round trip fares between Bangkok and Vientiane cost around 12'000 Baht, or if one wants to fly cheaper and doesn't mind to do some parts of the trip on the road, Thai Air Asia offers several daily flights to Udon Thani. Thai Air Asia offers round trips around 3'500 Baht.

A bus to the border at Nong Khai or even Vientiane is between 200 and 300 Baht... A good, reliable and low cost option...