I noticed this on the BBC. The University of Maryland has mapped global forest changes since 2000 based on landsat images. You can zoom into incredible detail for this type of study. Even in Thailand.
Its a great use of GIS and Google's APIs
I tend to stay away from making generalist comments in these matters but it seems to me that the obvious common theme in Thailand is encroachment and loss to humanist expansionism. All the RED areas that I can see that I know, have human populations in the those areas. Even though many of these areas have "small" populations, the effects are clear to see.
Nice to see a few BLUE areas also! The areas that I know mainly seem to be AA Paper's Eucalyptus planting program in Eastern Thailand though which is not forest. Some grow backs though in National Parks in Forest Parks and Thailand is way better than some of the neighbouring and regional countries. Cambodia is shocking!