Gilbert King is a writer for Smithsonian Magazine.

Ananda Mahidol was a slight and painfully shy boy. When he was nine years old in 1935, he became the eighth king of Siam and captured the hearts of his people. But his reign was painfully brief, ending in his bedroom with a single bullet fired into his head at close range. He was 20 years old. Within hours, Ananda’s 18-year-old brother, Bhumibol, ascended to the throne, where he sits today. He has ruled for 65 years, longer than any current head of state, and has amassed a fortune estimated at more than $30 billion, making him the wealthiest royal in the world. His spending on schools and hospitals, as well as on disaster relief efforts, have helped bolster his considerable popularity among his subjects. Ananda’s death, however, remains unsolved and largely unmentioned in Thailand today.

So what exactly happened in Thailand on that June morning in 1946?  The answer is no clearer today than it was in the immediate aftermath of a death that shocked Thailand and resonated around the world. Ananda and his brother had been inseparable as children and, by all accounts, remained close as they grew up. One of their common interests was firearms; they were known to take target practice on the Grand Palace grounds in Bangkok. On the morning of June 9, 1946, Bhumibol said he entered his brother’s bedroom chamber in the palace at 9:00 a.m., found him sleeping and left. Twenty minutes later, a gunshot echoed across the palace complex. The king’s page, Chit Singhaseni, rushed into the room and, seeing no one but Ananda, shouted, “The king has shot himself!” The king’s mother, Sangwal, followed the servant into the room. Ananda was lying in his bed, face up, with a bullet hole in his forehead and a Colt .45 pistol beside him on the bed. Sangwal pushed aside the mosquito net and threw herself onto the body, crying, “Alas, ‘Nanda, my son!”

The initial press reports out of Bangkok said Ananda’s death was accidental. “Diffident, bespectacled and boyish,” the New York Times reported, the king was “a fancier of firearms” and always kept a weapon near. Ananda had been within days of a trip to the United States for visits to New York and Washington, D.C., before returning to Switzerland, where he had received most of his education, to finish his studies for a law degree. The Times made a point of describing the worldly young king as “more Western than Eastern in his tastes,” as he “enjoyed playing a saxophone and driving an American jeep about the Palace grounds.”  In the days after his death, however, newspapers around the world raised the possibility that King Ananda had taken his own life. His relationship with a 21-year-old Swiss woman in Lausanne had broken off while he had returned to Thailand, and there were rumors that the king had been despondent. He was weakened by intestinal troubles, some reports said. He was a reluctant ruler and he’d been quarreling with his mother, noted others. But the Thai government quickly brushed aside any insinuation of suicide. It was simply inconceivable to the Buddhist people of Thailand that their enlightened king could kill himself. Besides, the government noted, the gun was discovered next to Ananda’s less dominant left hand, and the nearly blind king was not wearing his glasses when he died....