I was in Bangkok and Ayutthaya as well as some beaches a few weeks ago and for the whole 10days just had 1 Xt1 , 12mm samyang, 35f2 WR and 60mm ( Poorer mans setup :-) and all that did exceptionally well , i changed lenses alot i have a small shouder bag and can just grab whichever prime stick the camera in the bag and change lens , i didnt experience too much dust on my sensor, you can always get a few aps-c sensor swaps to pack with you if your worried about that :-)
Just have fun shooting and try to be as light weight as possible - If i had only 1 lens i would just bring the 23mm f1.4 ( I need to buy that ) or the 10-24 ( want that one too but more heavy ) but as of now i carry around the xt1 and 35f2 daily so lightweight i dont even bother with a bag :-)