Meeting one of the last women to be educated in one of Thailand’s royal palaces was a turning point for David Thompson. He was already in love with Thailand and its people, but he still clearly remembers the dish made by his Thai partner’s friend’s grandmother, Khun Sombat Janphetchara, that made him think “there’s more to this cooking than just making pad thai and red curries with chicken”.

“It was a sour orange curry over some deep fried pla chon [snakehead fish]. I can see it now, bubbling away, and I can almost taste it with fresh young tamarind leaves, whole red shallots and a vindictive amount of deep fried chilli on the top. It was just exquisite. This old woman cooked with the most incredible inherited skill,” says Thompson.

He never intended to cook Thai food professionally, but as he was then taking some time off, he thought he might as well learn all he could from this natural cook. Years later, he was the first person to receive a Michelin star for Thai food for nahm London, and now nahm in Bangkok is rated 13 on the World’s 50 Best Restaurants (Top 13) and No. 1 in Asia. He has become an active, and probably the best-known evangelist for Thai cuisine, which is famous for its emphasis on the balance of hot and sour, sweet and salty flavours. Thompson is so irreverent and energetic as we chat at lunchtime, that I wonder what he would be like after a few drinks, or after the two triple espressos that he has sitting in front of him. He has a reputation for not compromising on his food, and at a Sydney Good Food Month event the next day, I learn that he doesn’t compromise on his personality, either: what you see is what you get. During a cooking demonstration at the public event, he does a tequila shot delivered by another chef, swears a lot, and dares the presenter to eat a whole chilli (which he does with the usual face-pulling results). In conversation, he switches between self deprecating and arrogant in such a dry, voluble way, that it is at times hard to tell when he is being serious.

The Australian chef first became interested in cooking while finishing a degree in English literature. “I was about 22 and this genetic time bomb went off where I became obsessed with food. I just had to read and cook and taste and sample and it became a complete obsession, as if I’d found a home,” he says. He had already worked at (and got sacked from) a few Sydney restaurants before going on holiday to Thailand, and becoming enthralled by the culture. “I was seduced by the place. Not necessarily the food because I found it, like so many people, rather coarse and sharp and strong, overwhelming and also rather confusing. But it was the people, the edgy chaos, I found just delicious and exciting and thrilling and incomprehensible.”So in 1986, he moved to Thailand and started to set up a restaurant there, which didn’t work out. Despite the setback, Thompson decided to stay and take some time off, and it was then that he learned from the traditionally-trained Thai cook, and later returned to Sydney with his partner. He took over a restaurant at the back of a pub and called it Darley Street Thai (which he now calls a “bloodbath”). He says he cut his teeth there, but compares it to a fashion faux pas, like corduroy flares. “Looking back at Darley Street Thai, I think that it was clumsy and gauche in some of its dishes. It showed a cook that was beginning to understand a few things but to be honest I was probably still cooking Thai food like most Westerners do. I was a rather persistent little chappie… so with the keenness of a convert and the uncertainty of an outsider I investigated as much as I could.”

Thompson persevered, researched and improved, and part of that resulted in his weighty compendiumThai Food, released in 2002. After some success with Darley Street Thai and the more casual Sailor’s Thai in Sydney, he was invited to start a restaurant at The Halkin Hotel in London (“why not?” he says). Although he achieved success at the London nahm, including his first Michelin star in 2001, it was all too short lived. EU regulations restricted Asian agricultural imports because of poor labelling and traceability. Nahm lost about 70 per cent of their ingredients, and what they could get quadrupled in price. “[The staff ] would scour London in order to try and staple together some type of menu. It was just a desperate scramble… and affected everything,” he says. Bangkok nahm had recently started and had a cornucopia of ingredients in comparison. “I remember the thing that made me wriggle out of my contract was that we had two apple eggplants [aubergines] and they were wizened and old and the guys seized upon them as if they were rare gems. Two years ago we would have thrown them out as substandard. I thought ‘this is not the way to cook at all.’”

London nahm closed in 2012, and Thompson focused on the Bangkok counterpart, a slick, modern restaurant that occupies the ground floor of the Metropolitan hotel. Nahm’s reception in Bangkok was at first incredulous, not helped by a controversial interview Thompson did, he admits, as he got rather drunk with the journalist. He described Thai food as in decay, with fewer and fewer Thais cooking in the home. He also suggested that Thais had a broad repertoire and they could educate their guests by not cooking the cliché dishes. The interview resulted in outrage around the world, including of course in Thailand. “It came across as David Thompson thinks Thai food is no good any more, he’s here to open a restaurant to tell Thais how to cook… I made the joke that I’m the only person that can unite Thailand because they can unite together to tar and feather me and throw me out of the country.”

Although he may be provocative, no one can doubt Thompson’s devotion to Thai cuisine and people. “[Thais] have a very hearty and proper understanding of food. They don’t see it as a great art, they see it as a great craft. I agree. I’m very circumspect and suspicious of cooks that say that cooking is a great art and that it is akin to Mozart or whatever. At best, I think it engenders contentment which allows you to consider things with more equanimity than if you were bloody hungry.” Standout nahm dishes include a coconut and turmeric curry of blue swimmer crab or lemongrass salad with pork, prawns and squid. Although he has no favourite or signature dishes, he tells me of one that he is currently happy with. “It came by accident. It is a jungle curry of pla chon, the fish that I first had with Khun [his Thai mentor]. It was a green curry with green peppercorns, sour fruits and wild ginger. It was unusual, absolutely delicious and f ***ing hot. “I’d made it several times and played with it. I asked one of my guys to do the curry paste recipe for me and he accidentally made it not using the fresh green chilli but using red chilli. It was delicious, which made me muchmore annoyed with him. We played with it a bit more, made it with salted beef and served it with grilled eggs and rice. That combination at this stage is one that I completely like. In two week’s time… something else. There is such a vast, delicious repertoire.” He has always emphasised the difference between Thai food and street food which, as a hybrid of several cuisines, is “compromised”. “Thai food is pure Thai, eaten in a certain style whereas street food is a hybrid, a mixture of Thai, Chinese, Indian, Vietnamese, Indonesian… it is the most accessible, immediate and it is also the food that most people equate with Thai food, strangely enough. And it ain’t. That’s not to say it ain’t delicious.”

In 2015 he will be opening the street-food inspired Long Chim (meaning ‘come and sample’) at Marina Bay Sands in Singapore, with more of this style on the horizon in other locations. He says nahm is now part of the culinary landscape in Thailand, and taking it outside of the country would be a compromise. “Nahm will remain nahm; unalloyed Thai food, more formal and it does not compromise in its taste. My first priority with the food at nahm is to be faithful to the cuisine. I don’t want to sell people something that is adulterated. To me, that is not having integrity.”