The basic ones I've used for everything (flights and hotels) all have apps too!
Viator.com - trips and tours
-The above are very cheap ferry sites to get from island to Island and include bus transport in prices too well worth looking into. Easy to plan your trip by looking at the times too.
- this person has all the times and prices for buses and trains as well as other useful info.
Www.gadventures.com - trips and tours
Www.straytravel.asia - trips and tours
Our jungle house - tree houses and trips in khao sok national park
*** Another tip for Thailand is to watch people's travel vlogs they can help a lot !!!!
My basic itinerary for Thailand goes like this thanks to websites above.
Bangkok > boat cruise - best way to see hop on hop off - floating market tour - and basic wondering around. 2days
Bangkok > Chaing mai - 8days tour including overnight train both ways- Thai cooking class - hill tribe trek, bamboo rafting and an elephant ride with village overnight stay- shopping and back to Bangkok.
Chaing mai > Bangkok > Cambodia - 5 hour train to Aranyaprathet (48baht or £1)!!!! - sort visa at poppet and the onward travel to siem reap 2 1/2 hours aprox - visit to an amazing wonder Angkor wat then getting the train back the next day.
Cambodia > Bangkok > koh Samui - by ferry 10hours (£21.00) staying on koh Samui for 1night day and a half > khao sok national park 2nights 3days tree house stay and lake raft house stay inc actvitys and food. > Phuket and from hear I've not decided how long in places I want to stay but i will be staying in Phuket and the phi phi islands and doing island day trips and a visit to krabi/ ano nag beach.