Vienna Intl airport offers the cheapest routes to Bangkok, from ฿21,895; whereas Salzburg W.A. Mozart airport is typically cheaper if you're flying to Bangkok, from ฿23,205. It's best to make sure you are flexible on dates to find the cheapest possible flight options for your journey.
Here are some of the cheapest flight destinations from Austria:
Fly from Vienna to Bangkok from ฿21,895
Fly from Vienna to Phuket City from ฿21,895
Fly from Vienna to Krabi from ฿28,443
Fly from Vienna to Koh Samui from ฿28,880