This has been brewing for some time and now has come to a head.
http://www.bbc.com/news/world-asia-27517591
The relationship with China has always been an issue. Mainly regarding the status of Thailand as part of China. Or am I confusing it with another country?
This is part of it, but I do not think it is all of it.
http://www.cnn.com/2014/05/22/world/asia/thailand-martial-law/index.html?hpt=hp_t2