Numbers show number of tourist arrivals (in millions). Dates of political unrest and untoward events :
2009 : most negative events 11-12 April
2010 : most negative events : around 19 May
2011 : flooding of Central Thailand and part of Bangkok Oct-Dec
November 2013-May 2014 : political demonstrations, political upheaval Martial Law imposition 20 May 2014.
The first three quarters of 2014 saw a drop in arrivals when compared with the corresponding quarters in 2013 (-10,28% or about 2 million visitors less). However a few months after the military Coup d'Etat, during the final quarter of the year, tourism recovered.
The first two quarters of 2015 saw the highest number of arrivals ever, a good start to the year indeed.