Leaving non-Thailand politicians out of it, I think you would be hard pressed to name one non-corrupt Thai political leader since 1933. Thaksin gained immense popularity from the middle class and farmers because he promised to make their lives better and he delivered.
However, he angered military elites and others by indicating he was going to makes some fundamental changes. For instance, the head of the Privy Council (advisor to the monarch) was appointed by a top military official. Thaksin argued that this appointment should be made by the head of the civilian government, namely him. This irritated the military and other elites no end. They organised a coup charging Thaksin with corruption, an easy thing to prove, and anti-royalist sentiments (this did not seem to be true).
