On April 17, 1975, Kenneth T So – born So Khong Thay – saw the breaking news that Phnom Penh had fallen to the Khmer Rouge on a television in the canteen of the University of Tennessee, where he was studying chemical engineering.

The news horrified young So, who believed the rumours of Khmer Rouge atrocities, despite the dismissals in pro-communist periodicals. Like other Cambodians in the US at that time, he was worried about his family – his father, So Bun Hor, a businessman, and his two brothers, So Khong Leng and Chea Sophany, a police inspector and military physician, respectively.

Over the following months and years, news continued to trickle out the hermetic, ultra-Maoist state – of thousands of deaths from forced labour, starvation and mass killings by Khmer Rouge. A few years later, after the regime was ousted, So learned his brother Sophary was among the victims.

For the scientist-in-training, the tragedy triggered an interest in the history of Cambodia.

“I had not been interested in history until I realised about the Khmer Rouge’s mass violence,” So said this week. “I wanted to know where these black-shirt people came from and why they were so cruel to their own people, and it was not long before my interest went further and further.”

Despite struggling financially, So managed to complete his studies and graduate with a master’s degree from the University of Southern California and for the next 35 years he worked as a scientist for aerospace companies and NASA in the field of manned and unmanned space vehicles. During that time he also collected historical books and articles on Cambodia – and wrote a few historical articles himself. However, most of the works in his collection frustrated him.

“Most history books are written by Western writers, while most of their books contain too little information about many historical events in Cambodia, which makes it hard to understand,” So said. “I was so annoyed that the idea of writing a book with vivid details came to me.”

The idea stayed in the back of his mind for years, but So never had time to pursue it until his company transferred him to Colorado, in late 2007. The Rocky Mountain winters forced him to stay inside, but gave him the opportunity to take up writing. Now, nearly nine years later, his two-volume work The Khmer Kings and the History of Cambodia – comprising more than 800 pages – has just been released by DatAsia, a publishing company focusing on Southeast Asian nations.

The first volume centres on the beginnings of Khmer civilisation, starting in the first century with the early kingdom of Funan and continuing until the fall of the capital of Longvek in the 1590s to Siam, as Thailand was then called. The second volume picks up from the end of the first and continues up through the present day.

The books chronicle Cambodia’s relations with its neighbours, as well as the lives of everyday people and royals alike, with material drawn from the other writers’ works as well as So’s own research. So arrives at some new conclusions of his own based on his meticulous approach to historical material.

For instance, So studied ancient Chinese to better understand the account of Zhou Daguan, a Chinese diplomat who wrote about Cambodia during his stay at Angkor from 1296 to 1297. By closely parsing Zhou’s writings, he was able to compile a map of the ancient emissary’s travels in Cambodia.

Kent Davis, the publisher and editor for DatAsia Press, said he saw The Khmer Kings and the History of Cambodia as “a new standard”, and a reference for all other histories going forward, which no foreign writer could have produced.

“Ken drew from all the greatest scholars to assemble his text,” Davis said in an email. “But his qualities as a son of Cambodia and as a formally trained scientist with strong analytical and organizational skills are what set his vision apart.”

So’s academic background, nevertheless, could invite criticism, especially from established experts in the field.

Though he hadn’t read So’s books yet, Dr Michel Tranet, a prominent historian and author on Cambodia, argued that Cambodia’s history is more than “a pile of books and papers, and a bunch of pictures”.

“Writing a Khmer history book requires great knowledge of not only chronicles and the royal family but also the other fields, such as anthropology, astronomy, archaeology, horoscope and so on,” he said. “Those who do not have academic background in history, which requires learning all these, cannot write a real history book.”

However, Sophal Ear – an associate professor of diplomacy and world affairs at Occidental College in California, who has known So for years and co-written articles with him – supported his friend’s work.

“He has always been dedicated to Cambodia and its royal history from day one, along with origins of words like yuon, etc,” Sophal said in an email, referring to a controversial but widely used term for the Vietnamese. “If someone is passionate about something, they can learn enough on their own time to become an expert.”

Davis, of DatAsia, went even further in supporting So’s work, saying that he was completing history.

“What makes Khmer Kings great is that it is not purely academic history,” he explained. “Rather, Kenneth So offers readers a very personal tour of Cambodian history, with a guide who was nurtured in the language, culture and religion, and then educated as a scientist in the West”.

So, meanwhile, said he was already prepared for critical comments from historians, but maintained that his books would be a complement to other scholars’ works.“I did not do it for financial reward or fame,” he said. “I did it because I love my nation and wanted people to know more about it.”

The Khmer Kings and the History of Cambodia – Book I (364 pages) & II (440 pages) could be purchased by order on Amazon.com at $39.95 each or $79.90 together. According to the authors, they could be available soon at Monument Books.