Not sure about the rest of the Kingdom, but the "haze" is worst here in Isaan November to May. Everyone burns weeds in the dry season. The air clears nicely in rain season, and it isn't as hot as April (OMG). With everything being green and clean in rain season, May to end of September are my favorite times.
If you consider the 'Haze' as the early morning fog or as pre and after sunset 'dust' it is a part of my picture composition. In particular in Isaan, my beloved place for pre dawn shots.
See here:
www.fredmiranda.com/hosting/showgallery.php?cat=5176Hans