I was planning to take the route Bangkok, Vientiane, Hanoi, Ho Chi Minh City, Phnom Penh and back to Bangkok by air ( on average 80 USD type flights) However, The lack of cheap air tickets out of Vientiane restricted me to just two, namely Bangkok and Vientiane. This is probably because I wanted to travel North (Bangkok to Vientiane) first. How would you have done this trip on a 500 USD travel budget?