We figure that Thailand missed out on in between 1 and 2 million potential extra visitors in both 2009 and 2010. The same is probably true for end 2011 with the major floods, and end 2013-begin 2014 with the political uncertainty.
It is interesting to know that negative factors seem to loose influence in just 2 to 3 months each time, with visitors resuming their interest in Thailand as a major tourist destination thereafter.
Since end November 2014 till present (May 2014) there have been continuous anti-government demonstrations, led by former deputy prime minister Suthep Thaugsuban. The political upheaval surely affected the tourism industry, with various foreign goverments issuing travel warnings. The House of Representatives (Parliament) was dissolved on 9 December 2013. Elections were scheduled on 2 Februari 2014, but were disrupted and later invalidated by the Constitutional Court.