In the past eight years, the Thai military staged two military coups that overthrew two members of the Shanawatra family. Thaksin was toppled in 2006 and his sister, Yingluck, was removed from power in May this year. Obviously the military, which acts on behalf of the old establishment, had perceived the Shinawatras as a threat to its power position. And it felt that this threat had to be eliminated.
For decades, political power in Thailand had been dominated by the old establishment. But from 2001, when Thaksin strolled into the premiership, his overwhelming popularity with effective populist policies made him a champion of electoral politics. Ever since then the Thai political landscape has been transformed in a drastic manner. His political success was passed on to Yingluck, a relatively unknown member of the family. Winning a landslide election in 2011, Yingluck rose to become a popular leader in her own right.
The fact that Thailand is approaching a royal succession has deepened the anxiety of the old establishment that the Shinawatras could come back to politics and take charge of the transition inside the palace. This anxiety drove the military to oust Yingluck at the height of her political success.