Thailand’s spiciest plates are found down south.

ONE BALMY

tropical evening, my girlfriend, Michelle, and I sat down at Khao Horm, an unpretentious southern-Thai restaurant on the island of Koh Samui. When we asked the waiter what to order, he recommended one of the region’s greatest hits: kaeng som soup. “It’s spicy,” he told us, as though nothing more needed to be said.

“Can we order it mildly spicy?” I asked.

“No,” he said with a frown, flipping his pad shut.

“Okay, we’ll try it however you think best,” Michelle said. After we had grazed on bai liang pad khai—paper-thin, garlicky local greens stir-fried with scrambled egg—and moo pad kapi—pork in a shrimp paste strewn with whole red and green chillies—the kaeng som soup arrived. We could see, among the pieces of fresh fish and thin slices of green papaya floating in the ultra-tart tamarind-and-turmeric broth, an obscene quantity of chilli pepper. We both tried a spoonful. It was simultaneously spicier and sourer than any soup we’d ever tasted, the liquid practically searing our taste buds. But it was also so flavourful and satisfying that we had no choice but to keep eating it, spoonful after ridiculous spoonful.

We’d been warned about these soups in Bangkok, before we’d set out for the south. Prasert Sussadeewong, the executive chef at the

Mandarin Oriental Bangkok’s Sala Rim Naam restaurant, a professional in regional Thai cuisine, had just two words for me: “Be careful.”

Then he added, “There is a soup in the south that is so spicy that you take one spoonful and you stop...” The chef made a strangling gesture and shut his eyes.

“You stop what?” I asked. “Do you stop breathing?”

“No, you stop eating it,” he answered. “Immediately, you just stop.”

David Thompson, the author of the authoritative cookbook Thai Food and formerly the chef at the Michelin-starred Nahm restaurant in Bangkok, describes Thai cuisine as “irrational.” He means it in a good way. Its flavours are complicated, wild, and sophisticated—and southern Thai food is, without question, the most irrational of all. It isn’t just spicier than other Thai food; it’s sourer, sweeter, funkier, more coconutty. It’s also more eclectic. A meal in the region—whether on the street, in a home, or at a restaurant—can have Malay, Peranakan, Myanmarese, and Persian elements. The Portuguese, whose history in the area dates back to the

16th century, have also influenced the cuisine. And southern Thailand’s Muslim community, which amounts to about a quarter of the population, has added flavours and ingredients that go well beyond Massaman curry. Traders and missionaries of all backgrounds have settled in these temperate climes, which is why it isn’t unusual to come across Chinese-style pickled bamboo and plum sauce alongside Indian or Sri Lankan spices and biryanis.

Most Westerners have never heard of the region’s most iconic dishes: khua kling, a dry curry made with a kaleidoscope of fresh spices; moo hong, slow-braised pork belly rich in Peranakan Chinese seasoning; pla tod kamin, turmericcrusted whole fish topped with fried garlic. But a generation ago, most Westerners hadn’t heard of the pad thai–green curry–tom yum staples that are now ubiquitous in suburbs everywhere, and a decade ago, few had tasted the bold flavours of northern Thai regions like Chiang Mai and Isan, which have since been popularised by buzzy places like Pok Pok and Night & Market. Now, restaurants such as Kitchen 79, in New York City, and Jitlada, in LA, are betting that North American palates are ready for southern Thai food.

Certainly, Michelle’s and mine were. Michelle, whose mother is half-Thai and who loves green curry as much as I do, came up with the idea of seeking out these southern flavours at their source. That happens to be the beachy vision of the Malay Peninsula that most of us picture when we imagine visiting Thailand. This would be a trip in search of pure sensation, equal parts sunshine and spice.

We started on Koh Samui, a paradisiacal—and unsurprisingly, very popular—island off the eastern coast of the Thai mainland. Michelle and I were booked at Cape Fahn Hotel, a newly opened all-villa property on a small private island just off Koh Samui. Getting to the hotel requires crossing a narrow strait by one of two methods. When the tide is in, a motorboat whisks you over the waves, straight to reception. But when the tide is out, an amphibious truck with immense wheels simply drives over the sand and into the knee-deep shallows of the Gulf of Thailand. Driving across the ocean feels as wondrous as walking on water, and makes for a pretty memorable way to arrive.

After a day spent exploring the island’s palmtree-loaded beaches and luxuriating in our villa’s private pool, we were ready to leave the resort and head back to Koh Samui proper for some local food. Before our encounter with the fiery soup at Khao Horm, we drove to Bangrak Market, a seaside shopping area overflowing with fresh produce, seafood, and spices. It opens directly onto the water, so fishermen can bring their catch straight in from the sea. Across the street is a square that fills with street-food carts around

dinnertime. Among the vendors selling golden Buddha figurines, chefs in hijabs prepare fragrant, crispy rotis and dessert stands offer wobbly green jelly concoctions that taste like something from the future.

At Cape Fahn the next day, we learned about the incredible fruits produced by the country’s tropical climate, including mangosteens, rambutans, and durians, at a special guest activity: local fruit tasting. We learned how to sprinkle green mangoes with chilli salt to offset their sourness. We discovered that slivers of fresh jackfruit taste like Juicy Fruit gum, albeit with the texture of steamed chicken. And we learned to distinguish between langsats and longkongs—two types of fruit from the same species of tree, both of which contain translucent gummy-bearflavoured segments beneath a round, sandcoloured exterior. Put simply, the sort of next-level fruit knowledge that everyone deserves to gain while on vacation in Southeast Asia.

From Koh Samui, we flew across the Kra Isthmus—the Thai part of the Malay Peninsula— to Phuket, on the Andaman coast. From there we took a speedboat to Yao Noi, a tranquil, largely undeveloped island located among the extraordinarily photogenic limestone karsts of Phang Nga Bay National Park. We hadn’t realised ahead of time just how beautiful this part of the country would be—although anyone who has seen the James Bond movie The Man with the Golden Gun, which was filmed in the area, will recognise the stunning arrangements of emerald-shouldered islets rising from the turquoise waters.

One of the best views is from the Hilltop Reserve restaurant at the Six Senses resort, our lavish, sustainability-oriented hotel, which was designed to blend harmoniously with its environment. Our lodgings were as stunning as the setting itself, with their handmade wooden furniture, sunken bathtubs, and outdoor showers. And while the kitchen at Six Senses is geared toward a Western palate, those looking for classic Thai dishes will love the tom yum goong hot-andsour soup, as well as the banana-flower salad, which is topped with fresh mint, cilantro, and grated coconut.

In many ways a throwback to what Koh Samui was decades ago, Yao Noi is a sleepy, agriculturally minded place with a small, mainly Muslim population (only 4,000 or so people live on the island). Traditional homes on stilts stand over mangrove swamps rich with shellfish, while cows and water buffalo graze in the nearby rice paddies. Palm trees fringe the coastline, and the coconuts they produce are filled with a liquid that tastes as sweet as the palm sugar itself.

There isn’t much of a street-food scene, or a scene of any sort, for that matter—and that’s precisely the appeal. But should you need a break from staring at the karsts and the milky blue waters that surround them, there is one musttry restaurant located just around the corner from Six Senses. P’Chan is a simple spot attached to a general store where diners can sit on the sidewalk in the shade of an old jackfruit tree. The speciality is sea bass in lime sauce, a straightforward-sounding dish with a taste so vibrant it’s almost electric. The fillet of just-caught local fish arrives in a tangy green dressing spiked with orange bird’s-eye chillies, fresh herbs, and a great quantity of lime juice. Michelle suggested balancing the heat and sourness with cooling sips of iced tea sweetened with palm sugar and condensed milk. The combination was deliriously good.

Our final stop was Phuket, a large island across Phang Nga Bay, about an hour’s boat ride from Yao Noi. Although nearby, the island is very different. While Yao Noi is sleepy and undeveloped, Phuket was one of the first places in Thailand to experience a tourist boom. Today, it’s a frenetic take on paradise—a place to witness the country’s resort scene in all its neonlit, satay-scented glory. We were staying at the Rosewood Phuket near Patong Beach, one of the island’s busiest spots. Despite being so close to the action, the property’s location in the hills above a quiet cove and its guest rooms’ soft, neutral tones and floor-to-ceiling windows impart the feeling of a secret island getaway.

Best of all, the Rosewood is home to one of the island’s finest southern-Thai restaurants, so you don’t even need to leave the premises to have a perfect meal. Ta Khai occupies a series of repurposed traditional village houses—delightful wooden pavillions that are evidence of Rosewood’s obsessive quest for authenticity. The same impulse prompted the hotel to partner with Nun Rotkaew and Sangchan Suttitummanon, a husband-and-wife team from the Kra Isthmus, who have been perfecting their recipes together for three decades.

Uncle Nun and Aunt Yai, as the two are known here, met in their early 20s when she ate at the restaurant in Trang province, south of Phuket, where he was cooking. He made a crab fried rice she liked so much she asked him for the recipe. He offered to teach her to make it; they started a relationship, and from there, they began working together. “We are chefs in love for life,” Uncle Nun told me.

Michelle and I loved every thing we ate at Ta Khai, from the whole cracked crab with vermicelli to a fried rice not unlike the one that brought Uncle Nun and Aunt Yai together. A standout was fresh steamed fish with nam jim seafood sauce. “The queen of Qatar came here recently and liked that sauce so much she asked for the recipe,” he told me. Equally good was Aunt Yai’s dessert of steamed khanom tuay, a sweet dream of a pandan-flavoured coconut custard.

We didn’t get a chance to try their nam prik dip with fresh shrimp paste or their hor mok seafood custard, or many, many other dishes, for that matter. But by now it was clear: this was only the beginning. Just like Uncle Nun and Aunt Yai, we’d fallen hopelessly in love with southernThai food.

Khlong Toei Market, in Bangkok.