Thailand is a world recognized place of Tour and Vacation. Their are hundreds of flights to Thailand all over the world. It is well connected with non stop flights flights from Europe and US. Budget and package tours also available. May contact www.wordtravels.com/Travelguide/Countries/Thailand/CheapFlights.
For reguler flights best is http://www.thaiair.com/ the national carrier of the host country, as they know Thailand best.
Off course your national carrier like http://www.britishairways.com/travel/globalgateway from UK has also some package tours.
You may consult some other tour operators like http://www.aandftour.com/ for any better deals. 