For much of his career, the British journalist Andrew MacGregor Marshall has covered Southeast Asia for Thomson Reuters. During that time, he developed a particular fondness for Thailand, learning the language and falling for the “warmth and joie de vivre of the Thai people.” From 2000 to 2002, he was deputy chief of the wire’s Bangkok bureau, and in the years since he returned often, from his base in Singapore, to write about the political and social turmoil that roils the kingdom.

In June, though, Marshall quit Thomson Reuters after seventeen years to publish a three-hundred-plus-page story—on the Internet, for free—that has made him a wanted man in his beloved Thailand and will likely prevent him from safely returning there for years. “People thought I was crazy,” says Marshall, not to be confused with the Andrew Marshall who is Time’s Southeast Asia correspondent. “They probably still think I’m crazy.”

There is, however, a method to Marshall’s madness. He had grown increasingly frustrated at his inability, and that of journalism generally, to tell the full and honest story of the kingdom’s ongoing political crisis, which at its core is about the unspoken role the monarchy plays in the politics of a country that claims to be a free and functioning democracy. This crisis produced a military coup in 2006, and street protests and occasional violence ever since.

Thailand is a country that runs on rumor, due to a chilling trifecta of laws: defamation, the computer crimes act, and a draconian lèse majesté law that makes it illegal to insult the monarchy. Together, they criminalize essentially all candid public discussion of politics and power in the kingdom and make serious reporting all but impossible. (I ran afoul of Thai press laws, too, in 2009, and had to flee the country. You can read my story at cjr.org/behind_the_news/fry_in_thailand.php.) Marshall calls Thailand a country of secrets and describes reporting there as an exercise in taking “baby steps” towards truth.

That changed dramatically for him in March, when Reuters gained access to the trove of 250,000 secret US diplomatic cables that WikiLeaks dumped on the world in November 2010. Marshall homed in on the three thousand cables that pertained to Thailand, which the rest of the journalism world had mostly ignored. “The cables went far beyond baby steps,” he says. “They just ripped everything wide open.”

He knew he had a story that Reuters would never publish, and that he would need to leave the company to write. (Reuters has publicly stated that it could not publish the work because of “questions regarding length, sourcing, objectivity, and legal issues.”) Marshall left with copies of the cables—the cache from Thailand, but other countries too—a decision that strained his relationship with Reuters, but which he justifies as being in the spirit of the information and transparency. “I never wanted to put my colleagues in danger,” he says. “I was doing it because I believed in journalism and that I could do some good.”

Marshall has published two parts of his four part story, entitled “Thailand’s Moment of Truth: A Secret History of 21st Century Siam,” and plans to publish parts three and four soon. It draws largely on these cables, complemented by his own reporting. It offers an account of Thailand’s recent troubles that is unprecedented in its scope and candor, reaching back through the country’s history to provide insight into the current situation. Marshall dissects the messy political and royal dynamics. He depicts the kingdom in the throes of a behind-the-scenes power struggle and succession crisis that continues to mount as the much-revered but ailing King Bhumibol fades from relevance in a Bangkok hospital.

According to the cables, King Bhumibol, who has spent the past two years in the hospital for mysterious but reportedly unserious reasons, suffers from Parkinson’s disease and depression. The cables suggest he is largely estranged from his wife, the Queen, who has assumed his power and, with a coterie of loyal military officers, become the real force in Thai politics—“the invisible hand” that orchestrated the 2006 coup, the paramilitary build-up in Thailand’s south, and the “yellow shirt” protest movement against former Prime Minister Thaksin Shinawatra. Meanwhile, Bhumibol’s heir, the Crown Prince, who is regarded by most Thais as a loathsome playboy, comes across in the cables as exactly that. His dog, Foo Foo—who is also officially a Thai Air Marshall—laps at the US ambassador’s plate in one memorable scene.

Erika Fry is a former assistant editor at CJR.