On the morning of June 9, 1946, the 20-year-old Ananda Mahidol, King Rama VIII of Siam, was shot through the head and killed in his bedroom in the Barompiman Hall building in the Grand Palace complex in Bangkok. Later that day his 18-year-old brother Bhumibol Adulyadej was proclaimed King Rama IX.

Officially, the killing is described as a mystery, one o…