The rapid shrinking of Cambodia’s linguistic diversity is, sadly, not a matter of common knowledge. Of the 24 native languages currently spoken within the country’s borders, UNESCO estimates that 19 will cease to exist by the end of the century.

According to veteran linguist Gerard Diffloth, their extinction will result in an inestimable loss to historical research.

“Unfortunately, the history that is written is all based on the history of people who have writing, who have books, inscriptions, and systems of government,” says Professor Diffloth. “All the history that is written is always almost completely focused on those kinds of people. And these people are totally ignorant of people without written language, as if they have no history, which is wrong. They have a history as long and as complicated as anybody else.”

Diffloth has devoted the past three decades of his career to a meticulous study of the Kuay language group, most commonly found in Thailand, Cambodia and Laos. Though the Kuay lack a system of writing to record their exploits for posterity, linguistic and archaeological research has helped to unearth their pivotal and underappreciated role in the region’s wider history; Diffloth is passionate about the picture this research has painted.

“For instance, the Kuay had, in the past, a monopoly on smelting iron in Cambodia,” Diffloth says. “Forging iron is very easy. Smelting it is a very difficult, much more technical question. This monopoly is finished; the Kuay don’t know how to smelt iron anymore. But 50 years ago there were people who still knew how to do it.

“Recently we’ve discovered huge remnants of this smelting history. There are hills and hills and hills of slag left over from the process, so this wasn’t just a cottage industry. Almost certainly it goes back to Angkorian times and maybe even before that. So if you think about that, obviously they must have had a very big role in Cambodian history. Just look at the bas-relief in Angkor Wat, and how many weapons can you see?”

Diffloth first came to Cambodia in 1965 for a brief sojourn following the completion of his PhD research into languages descended from Tamil on part of the Indian subcontinent. After studying the Kuay in Thailand, he was invited back in the early 90s.

At the time, the United Nations Transitional Authority in Cambodia was preparing for the 1993 elections, and found itself hamstrung by the lack of scholarship on the country’s minority languages.

“Before independence, people knew that these ethnic groups existed and were different from the Khmer; it was not unknown,” he says. “In those days, the French were very interested in the people of the eastern provinces because they were raising coffee plantations there.

“After the UN came, they suddenly realised they had minorities in Cambodia, not just Vietnamese or Chinese, but very small minorities,” he says. “They wanted a report to know where they were and what kind of lives they were living. So I wrote this for them, and of course it was very interesting to be here at that time.”

It may be more the result of half a century of experience in the field, but Diffloth is charmingly nonchalant about what seems to be a colossal endeavour.

Last year, he wrote a book cataloguing an extensive array of Kuay words in the International Phonetic Alphabet. His research took him through four of Cambodia’s northern provinces and involved extensive periods of time embedded in Kuay communities.

“A lot of their reaction depends on your own behaviour. If you arrive there in a way they don’t like then they won’t like you, that’s the end of that. But you have to tell them what you’re doing there; you’re not going to cheat them. You have to be straight and say that’s what you want to do. They judge you very quickly as to whether you’re a decent person or not. Not that I’m a decent person,” he laughs.