The Office of Tourism Development website has recently been updated and shows arrival statistics. The excel files on the website provide data in English, just follow the 'Statistics' link.
It is safe to say that health scares and the global recession had a more pronounced impact than the local political uncertainly, riots and demonstration. Thailand experiences an unstable political scene, but overall fortunately the tourism industry continues to grow with a moderate hick-up during the first three quarters of 2014. Visitors picked up again at the end of 2014 and kept on rising in 2015.