The Business of Buddhism" and their baseless claim that there are about 120,000 monks in Thailand down from 300,000 some years ago. I then researched more claims of monk numbers in the Kingdom and now thanks to Frank at the Korat post now have numbers from the Office National Buddhism that presents numbers by province since 2547BE. If you do not read Thai Google translate will help you see where to choose the year you are interested in and as you can see the total for 2554, last year is a total of 290,331 Mahanikaiy and Dhammayut monks in the 76 provinces plus Bangkok., a bit more than the 120,000 guess by the Bankok Post. I believe this census includes ID card carrying monks, not short time monks.
This information along with the list of Monasteries, listed by Jangwat should give a person a pretty good view of the numbers relative to the Sangha and their places in Thailand