“Thai cuisine, you know, it’s supposed to hurt a little,” Pim Techamuanvivit, the chef at San Francisco’s Kin Khao and Bangkok’s Nahm, had told me. “But there’s definitely a balance between using chile and allowing the other flavors and the true nature of the ingredients to show themselves.” I would have to be careful not to let my quest for fire get in the way of my quest for enlightenment. Any dumb farang — i.e., foreigner — could burn his face off; I wanted something more nuanced, to burn with understanding.

One Sunday morning, a quick ferry ride across the Chao Phraya River from Err, the Church of Santa Cruz was alive with activity. A pale blue sky hung over the century-old Italianate church — peachy yellow with pink accents and a red-domed steeple — while inside dozens of worshipers sang hymns in Thai and listened to a priest’s sermon from the gold-adorned chancel. They were young and old, some dressed up, most casual, all members of the 200 or so families that make up the surrounding community — a community that is not only Catholic, with crosses and images of the Holy Family adorning their homes, but Portuguese.

Historically, anyway. This neighborhood was Kudichin, and it was about as close as I was going to get to envisioning the first contacts between Thailand and the Portuguese. The neighborhood was created in 1769, when King Taksin granted land to three groups that had aided Siam in war with Burma. It was a war that Siam basically lost: The Burmese looted and burned the royal capital, Ayutthaya, 50 miles north, where the Portuguese and other foreigners had encampments. Siam’s leaders retreated to Bangkok, and the Portuguese, along with the Chinese and a group of Muslims, now had land to call their own, here on these flood-prone mud flats.

Two and a half centuries later, the community has managed to preserve some Portuguese culinary traditions. At the airy café of the Baan Kudichin Museum, I snacked on sappayak, a light and yummy baked Portuguese bun stuffed with sweet minced pork, potatoes, curry powder, and red flecks of mild chiles. And after Sunday mass, a street stall behind the church sold a very Portuguese beef stew with potatoes and tomatoes (both New World crops!), as well as sweet, Chinese-­influenced pork, braised with soy sauce, tofu, and hard-cooked eggs, and a fiery Thai curry of ground pork and pea-size eggplants that popped with tart astringency. Eating all three together felt like communion with history, as if the groups that had created modern Thai cuisine were right there at this folding metal table at the edge of the street.

Spicy ground pork stir-fried with holy basil.

The exact moment chiles arrived in Siam may have been lost to history. Foreign visitors’ accounts offer tantalizing threads. Portuguese apothecary Tomé Pires visited Siam around 1514 and wrote of rice and pepper, and a 1688 account by the French Jesuit Nicolas Gervaise mentions pepper but not peppers. (He also berates Siam’s “stupid cooks” and their shrimp paste, “which has such a pungent smell that it nauseates anyone not accustomed to it.”)

But what is certain is that over the past 500 years, Thailand’s chiles have flourished in dizzying variety. Today, there are prik kee noo suan, or mouse-shit chiles, skinny and hot and known in America simply as “Thai chiles.” (English spellings of Thai pepper names may differ depending on source.) Prik chee fah, or sky-pointing chiles, are longer and milder, growing up from bushes instead of dangling. Prik som are orange and meaty. Prik kaleang, the chiles named for the Karen hill tribe, may be the hottest of all, but they were not included in a 2008 Kasetsart University study that measured the pungency of Thai chiles and rated most between 45,000 and 80,000 Scoville units, at least 10 times hotter than jalapeños. Of course, that’s just the beginning. Trying to track down every variant, when flavors and names proliferate and overlap, is a fool’s errand.

Which is how this fool came to be in Phatthalung, about 500 miles south of Bangkok, closer to Melaka than to the Thai capital. On the west the district was bordered by greenish limestone mountains that erupted from the rice-paddied plains; to the east was Thailand’s biggest lake, and beyond the lake the sea. Whichever direction I looked was pure Thai picturesqueness.

Fields of prik khao chi in Phatthalung.

Loveliest of all was right before me: two long fields of prik khao chi, a relatively rare variety of chile known as “white nuns” because they don’t redden when ripe. On the bush, they were a very pale yellow, skinny and wrinkly and crooked, and when I nibbled one it gave off a ton of heat and a fresh, bright aroma that was, I’d been told, essential to southern cuisine, which is known not just for its intense fire but for its sourness and fermented fishiness. The night before, at the quiet lakeside restaurant Kieng Talay, I’d dived headlong into those flavors — a tart and crunchy lotus-shoot salad, soupy-shrimpy curries with crabmeat or ­whisker ­ sheatfish — until a pleasant funk lodged in my nostrils and my throat burned and lips puckered. The heat had taken its time building, a signature southern style derived from local chiles.

These white nuns had been grown by Vichit Janphaleuk, who was 64, with wavy hair just going gray and a loose checked shirt, and who’d specifically chosen to farm chiles 30 years ago. It was a decision born of practicality.

“This area is going to be flooded every year,” he said through a translator, “so if I grow something else, it’s going to be flooded before I even sell it.” With chiles, he can harvest about 100 kilos a week of the fast-growing crop from May until the floods hit in November.

Thai proverb: “Bring all the chiles from the plantation.” Meaning: You’re looking super-sexy.

But growing chiles, he’d also come to realize, is more than a business — he sees it as a responsibility. “Because everyone eats chiles in daily life,” he told me, “I need to make high-quality chiles, clean chiles, to feed everybody — maybe around the world!”

That’s not to say it’s an easy business. Currently, Vichit sells his prik khao chi for around 45 baht per kilogram, or about $1.50. That seems decent, but a few years back, he said, the price was 200 baht per kilo. Meanwhile, he had a half-field of prik kee noo he wasn’t even bothering to harvest — the price was simply too low.

Because out in the countryside, everyone had chiles already. They’d been planted around the house I rented nearby, and they grew wild, too. A bird poops in your yard, and — boom! — you’re growing prik kee noo, wild bird-poop chiles. Maybe you’d farm prik khao chi for restaurants or city-dwellers, but for many Thais, it doesn’t make sense to spend hard-earned money on what’s freely available out back. Spice is spice is spice.

Well, sort of. Slightly more than 24 hours later, at the opposite end of Thailand, I was facing down a fundamental challenge to that idea, put together by the young, round-faced chef Weerawat “Num” Triyasenawat in the narrow kitchen of his ambitious restaurant, Samuay & Sons, in Udon Thani. On the counter before us lay five bowls of som tam, the mortar-pounded salad of shredded green papaya, chiles, and fermented fish paste that is an icon of Isaan, this inland region along the northeast border with Laos. Som tam is also iconically incendiary: You sometimes order it with a number indicating how many chiles to include.

That night, however, we were not just testing our (okay, my) chile tolerance but trying to figure out which variety of chile worked best. Each bowl had been prepared identically, but with different peppers — prik kee noo suan, prik leung, prik jinda dang, and smoked prik kaleang; the final bowl contained all of the above. Along with Num and me, the judges included three of his female cooks, who giggled as I reached out with my bare hand, pinched a bundle of papaya from the first som tam, and popped it gamely in my mouth. Unlike in the south, with its slow-to-build fire, Isaan-style heat hits you right up front, repeatedly, like a Thai kickboxer out for a quick win. Behind each beautiful capsaicin burst lay subtleties — the invigorating freshness of the prik leung, the meaty-smokiness of the prik kaleang. By the end, I was dripping sweat.

Outside the Church of Santa Cruz.

Heat had been a factor in Isaan cooking for ages, Num told me: “Before the chile came to our region, people in ancient times used pepperwood to spice up the dish,” along with makhwaen, Krachai, and long pepper. (Southern spices like cinnamon and cloves were too expensive for isolated Isaan.) But heat was never just for heat’s sake. It worked in concert with the vast orchestra of ingredients found only in this region, many of which I’d never seen before: herbs that were peppery, astringent, lemony, obscure, addictive; foraged mushrooms as dainty as daisies or as massive as porcini; hairy tomatoes.

In fact, this was the whole point of Samuay & Sons, whose tasting menu I leapt into as soon as I’d finished with the som tam. Each of chef Num’s seven courses highlighted Isaan-­specific ingredients and flavors, alongside the world-class technique he’d honed at San Francisco’s Michelin-starred Commonwealth. Meaty, thin-shaved prawns were tiled next to a pool of smoked pineapple curry; a morsel of chicken, mango, and yellow curry punched way above its weight. I adored a dense block of “soured fish confit” — fermenty and rich — and its miraculously cooling accompaniment, rice in a watermelon consommé.

Chiles were in there, too, but harder to pinpoint. At first I worried that the som tam taste test had blown out my palate. But no — that spice bath had only sharpened my senses. Chef Num had achieved the type of balance that Pim had described to me before I’d set off, deploying chiles that “hurt a little” but then stood humbly aside to let the true stars shine.

Malaysian proverb: “He who eats chiles gets burned.” Meaning: Actions have consequences.

WHEN I RETURNED TO BANGKOK, I felt like I was finally getting a handle on the chilefication of this country. Peppers likely came to Siam in the 16th century, brought by the Portuguese and, later, the Spanish. They took off because people were primed to like spice and because chiles grew easily, even wild, so everyone could afford them. Now they were ubiquitous, essential components of every strain of regional Thai cuisine, and getting more popular by the day. (Sugar may have something to do with this. Since the 1930s, its price has dropped. Sugar tends to tame chile heat, so the sweeter the dish, the more chiles you can add. This theory dovetailed with Pim Techamuanvivit’s complaint that the food in Bangkok has gotten too sugary since her childhood.) A film director, I’d heard, was planning a movie about chileheads, and a candy company was selling “Hell Spicy Jelly,” jelly beans that contained Carolina Reapers, one of the world’s spiciest peppers.

The future began to look even more fiery one Friday, when I traveled about 100 miles west from Bangkok to the edge of Kaeng Krachan National Park. Just as a soft rain began to fall, I arrived at the farm of Prew Pirom, the 41-year-old owner of Pla Dib, a Bangkok restaurant that happens to be my all-time favorite. Prew wore a broad hat and a round-cheeked, persistent smile as he showed me around: his small, chic home adapted from shipping containers; a pond for raising catfish. Citrus and other fruit trees surrounded half a dozen airy greenhouses, inside which grew eggplants, cucumbers, tomatoes, lettuces, and chiles. Scotch bonnets, to be precise. I did a double take. Jamaica’s pride, here in Thailand?

The seeds, Prew explained, were gifts from two foreign friends who’d picked them up in Jamaica. He grew them, offered the chiles to customers on pizza, integrated them into Thai dishes like braised pork leg, and fermented them into a sparkly, fiery sauce — finally, he had a chile that was hot enough for his taste. His capsaicin tolerance, he said, was above average. (Every other Thai I asked said the exact same thing.)

Chiles by the Numbers

Annual per-capita consumption of chiles and green peppers in Mexico: 15.49 kilograms In China: 11.58 kilograms In the United States: 2.79 kilograms In Turkey: 26.79 kilograms Estimated size of U.S. hot sauce industry in 2018: $1.5 billion Projected size in 2023: $2 billion Heaviest chile pepper: 0.77 lbs Longest chile pepper: 17.72 in

Fire breather Vichit Janphaleuk assesses one of his peppers.

Scotch bonnets, I figured, should have great potential in Thailand, but could they take off? Whoever tried one, Prew posited, would like it. Perhaps he could let birds feast on his Scotch bonnets and have them spread the seeds far and wide. It worked in the 16th century; why not now?

Before that future arrives, though, he’s got to stabilize his crops. Some of the pepper plants he showed me were small, their leaves a mottled white and yellow, victims of a disease he said had afflicted all peppers in the area. Just like the farmers in Jamaica, Prew was facing the double-edged sword of a warm, moist climate. But then, I thought, maybe a Thai problem needs a Jamaican solution! Right away, I fired off a WhatsApp message to Gary Coulton — could his high-quality seeds help? Could I put him in touch with Prew?

“As we say in Jamaica,” Gary wrote back, “‘NO PROBLEM, MAN.’”

Finally, it felt like I was no longer chasing history but right in the middle of it. Chiles may have begun their planet-spanning voyage half a millennium ago, but they were nowhere near finished — there were always new lands to conquer, new palates to convert, new routes to crisscross and double back on, new mashups of heat profiles to set afire even the smallest acre of bland land. The world is burning, my friends, and it’s our delicious privilege — in my case, a duty! — to add fuel to that fire.