Laos Airlines flies from Vientiane to Houeisay. You would have to first fly from Phuket to BKK, then BKK to Vientiane (or take buses and trains).
You can also fly with Bangkok Airways from Phuket to Luang Prabang and then take the boat the opposite way.
#2 guava_girl has been a member since 21/10/2010. Posts: 252
Nope. No customs/immigration. You have to fly into Vientiane first, then fly to Huay Xai. Could be quite expensive and/or time-consuming.
You'd probably be better off flying to Chiangmai from Phuket, and then taking the bus to Chiang Khong.