Appetite for adventure

"In Thailand a few generations ago, cooking was a major occupation," Thompson says the next day as we head across the city in a bright-pink taxi to source ingredients for Nahm at Or Tor Kor Market. "These days, all Thais know about food - and for many it's all they think about - but few people want to, or have to, cook. Instead they rely upon the fruits of the street."

Street food emerged in Bangkok through the mass migration of Chinese itinerant workers in the 19th century, Thompson says. Most of these Chinese men didn't have, or couldn't afford, kitchens, which created demand for ready-made meals. Mass urbanisation and changes in gender roles during the 1960s, when women began to enter the workforce, accelerated this trend.

These days there is an entire culture built around street food. It's rare to find a street corner that isn't swarming with makeshift trolleys manned by cooks preparing steaming bowls of noodle soup or barbecued chicken with a feisty dipping sauce. Most stalls serve only one or two dishes but these are prepared exceptionally well.

"The most interesting thing about Thai street food is that very little of it is Thai," Thompson says. Most are variations of dishes originating in nearby countries: Malaysia, India and China. Even Thailand's legendary pad Thai (rice noodles stir-fried with egg, shallots, bean sprouts and firm tofu) is based on a Chinese dish and modified with Thai spices.

We spend an hour scouring the market and jostling with the unyielding market women presiding over jars of pickled ginger and vats of pungent shrimp paste ("Would you argue with her?" Thompson chuckles at one stall). Or Tor Kor, near the bustling Weekend Market otherwise known as Chatuchak, on the northern outskirts of the city, is by no means the most convenient wet market in Bangkok, nor is it the cheapest. But, for Thompson, it has the plumpest, freshest produce available and this is where he'll be sourcing the majority of Nahm's ingredients. "It's just fabulous to have such a rich array of quality produce on your doorstep," he says, inspecting a smoked mackerel. "In London we have to fly everything in … and some things you just can't get past the border."

For lunch, we buy a few dishes from the "ready-made" section of the market, then order fresh noodles and bottles of sugarcane juice and find a table at the market's canteen to eat. There is a superb pat pet luk chin plaa graai (red curry with featherback fish dumplings and eggplant), gung pat sadtor or "stinky beans" ("because of the way the toilet smells the next day") with prawn and calorific pork sausages, which we devour with raw bird's-eye chillies.

Thompson's arrival in Bangkok in 1986 was serendipitous. A chef in Sydney at the time, he had been planning to head to Tahiti with friends for a holiday. When his friends cancelled suddenly, a Thai kitchenhand convinced him to go to Bangkok instead. "The city was a lot more edgy and dangerous back then but I just fell in love - the languid savoir-faire attitude to life; the Buddhist idea that all living is transitory and so should be savoured and enjoyed," he says. "I spent the next two years squandering my savings in Bangkok, which turned out to be a pretty good investment. The rest is history."

On his birthday, in "a disreputable Bangkok bar where old queens go to die", he met Tanongsak Yordwai, his partner of 23 years. In 1991, he opened the landmark Sydney restaurant, Darley Street Thai, in a pub in "the wrong end of Newtown" and Nahm in London in July 2001. In the process, he has developed a deep affection for Thai people, their tonal language and their inimitable cuisine. "I think Bangkok has softened me considerably," he says, offering me the last pork sausage. "It has taught me that there are some things that you just can't change and any urgency that you may have shouldn't be at the expense of other people."

Thompson's favourite Thai food will be showcased at the new Nahm, a small but subdued diner with wooden tables separated by low-slung dividers and raw-brick pillars, mimicking the temples of Thailand's former capital, Ayutthaya.

The next day, Thompson is testing one of Nahm's degustation menus on the hotel staff ("From cleaners to kitchen hands, I want them all to experience and be part of the restaurant") and I manage to score a place at the table.

The feast begins with parboiled quail eggs topped with a smoky chilli relish and wafer-thin crisps filled with chopped prawn meat and bean sprouts. The main courses are placed in the middle of the table and shared Thai style. There is a lemon grass salad with minced pork, a sour tamarind curry with river prawns and a delectable stir-fry of baby squid with snap peas. The dishes are full-bodied and encompass the full spectrum of tastes: sweet, salty, sour and astringent. Mercifully, they are milder than my last meal cooked by Thompson, which left my mouth burning for hours.

I ask the staff how they feel about a non-Thai being an expert on their own cuisine but they are too polite to give me a straight answer. How does Thompson think they feel? "Incredulous," he replies. "I also feel this when I see a Westerner cooking Thai food.

"The best compliment I have ever had was from the wife of a Thai minister who came to eat at Nahm in London. Literally scowling, she came to me as she was leaving and said, 'I came in to complain about the food but I can't'."

Thompson says many restaurants in Thailand "just dress up" for tourists, as Thai cooks modify dishes in ways they think will satisfy foreigners. "Thai food is becoming milder, sweeter - although you can still go to the countryside and get a wallop. I want this Nahm to be as authentic as possible."

Does Thompson have any advice for travellers apprehensive about eating street food? "Get over it," he says. "Thais go to the market each morning. Everything is super fresh and spends less than eight hours between being picked and landing on a plate. They have never died from eating their food and neither will you."

There are a few universal rules. Eat where the locals are eating; there is usually a reason that street stalls, like restaurants, are busy, or empty.

Unseasoned Asian travellers are wise to stick to freshly prepared and hot food. Don't hesitate to check the cleanliness of the stall before ordering your food. And go easy on the chillies if you're not used to them; the tiny bird's-eye ones are incendiary.

Or, if in doubt, head to the new Nahm.

Leisa Tyler stayed in Bangkok courtesy of the Metropolitan Bangkok hotel.

THE CHEF'S CITY GUIDE

Eating there

Apsorn's Kitchen for crab in curry powder, deep-fried kingfish with green mango and yellow curry with prawns and lotus shoots. At Samsen Road, near the National Library; +66 2 668 8788; open for lunch and early dinner.

Muslim Restaurant is one of the oldest continuously running restaurants in the city, and serves a magnificent Penang beef curry for lunch - it's rich and red and redolent of cumin. At 1217-9 New Road, Bangkrak; +66 2 233 1010.

Baan Klang Nam for great seafood, such as deep-fried grouper, grilled prawns and squid deep-fried with garlic and crunchy grilled pork jowls. Ask for Bom, the kind and knowledgeable manager. At 288 Soi 14, Rama III Road, +66 2 292 0175.

Suan Luang night market for grilled chicken and fish and pork wonton soup. The chicken stall is open only on Saturday evenings but the fish dumplings are available all week. For dessert, hop next door for combinations of black sticky rice, sliced jackfruit, palm-sugar seeds, dried lychees and pandanus noodles. At Soi Chula 18, behind Chulalongkorn University; no telephone.

Bo.lan is a fascinating Thai restaurant run by Bangkok-born Bo and Melbourne-born Dylan, two cooks who worked with me at Nahm in London. Try the grilled beef curry in cassia leaves and minced prawns simmered in coconut cream. At 42 Sukhumvit 26; +66 2 2602 9623; www.bolan.co.th.

Mei Jiang at the Peninsula Hotel for classy dim sum. I love the rolled noodles with black beans and chillies and I swoon over the drunken noodles. At 333 Charoennakorn Road, Klongsan, Bangkok, +66 2 861 2888; www.peninsula.com.

Pranakorn Bar is an eccentric bar upstairs from a dingy restaurant but with a magical view of the Golden Mound, an old temple. The drinks are OK; the music can be good; but it is the quirkiness that I like. At 58/2 Soi Damnoen Klang Tai, off Ratchadamnoen Road; +66 2 222 0282.

The Long Table is a newish bar with good cocktails and fabulous views over the city. At 25th Floor, 48 Column Building, Sukhumvit Soi 16; +66 2 302 2557; www.longtablebangkok.com.

David Thompson's new Bangkok restaurant, Nahm, is scheduled to open later this month at the Metropolitan hotel. Phone +66 2 625 3333 for bookings. His hardback cookbook, Thai Street Food, is published by Penguin ($100).

Shopping there

Or Tor Kor Market near the Weekend Market (also known as Chatuchak) has some of the city's best produce as well as a fantastic Isaan sausage shop that you should try with whole birds-eye chillies. On the weekend you can visit Or Tor Kor Market, then cross the street and spend the afternoon wandering through the Weekend Market, a wild, crowded jumble of bars, clothes, antiques and almost everything else you can imagine.

Sleeping there

Metropolitan Bangkok hotel is a suave city hotel with a great spa and friendly staff. Double rooms from 2800 baht ($97) in August and September, see metropolitan.bangkok.como.bz.

Chakrabongse Villas is an old palace with a few guest rooms. Sit in its pavilion on the water, opposite the Temple of the Dawn, and watch Bangkok float by. Suites from 8000 baht, at 396 Maharaj Road, Tatien; see www.thaivillas.com.

Getting there

Thai Airways flies non-stop to Bangkok from Sydney and Melbourne (9hr) for about $1150, low-season return, including tax. Qantas flies non-stop from Sydney; Jetstar flies non-stop from Melbourne.