"What's the first designer item you ever bought?" I ask 42-year-old Vietnamese tycoon Le Hong Thuy Tien as we cruise through Ho Chi Minh City in her beast-like black Bentley. It has come to this. I have been asking about her childhood during the Vietnam War (or the American War, as it's known here) for the past half an hour. She has politely refused to be drawn. Fawning questions about how filthy rich she is are all I have left.

"That's a great question!" she exclaims, her perfect eyebrows arching with delight. Sadly, it is only half great. The purchase was so many hundreds of Louis Vuitton tote bags, Bulgari watches and Chanel dresses ago that Thuy Tien can't remember the answer. She searches her memory in vain as motorcycles buzz past like flies outside the tinted windows.

Whatever the item was, we establish that she most likely bought it in Paris in the mid-1990s. Back then she was a flight attendant for the national carrier Vietnam Airlines. It was such a coveted job at a time when few Vietnamese could travel that she'd chosen it over a fledgling career as a movie starlet. Today she is the president of a huge trading company, Imex Pan Pacific Group. "I run 25 private equity and venture capital firms that distribute luxury brands and invest in local shopping malls," she says in her girlish, slightly Americanised English.

Unlike some of Vietnam's super-rich, who are reluctant to flaunt their success in a country run by an increasingly jittery and repressive Communist regime, Thuy Tien is all about the money. Her mission, she adds, is to generate annual revenue of US$1bn. How close is she? "I'm over half way there."

Welcome to modern Vietnam – one side of it, at least – where the pinnacle of achievement is to snare the exclusive rights to distribute Burberry or (Thuy Tien's newest acquisition) the franchise for Dunkin' Donuts. The city formerly known as Saigon was renamed Ho Chi Minh City to celebrate national unity after two decades of civil strife, including the war with America from 1965-75. Now it is Vietnam's commercial hub. Gleaming billboards and five-star hotels signal the country's status as Asia's fastest-growing economy after China. Since liberalisation began in the 1980s, founding father Ho's Communist mantra "Success, Success, Great Success" has become the creed of hardcore capitalism.

The number of multimillionaires has jumped 150% in the past five years alone. There is no breakdown by gender, probably because women like Thuy Tien are still rare. Vietnam remains overwhelmingly male-dominated. There is only one woman in the 14-member ruling Communist politburo and overall equality is badly lacking. Problems such as bride trafficking and forced prostitution are rife. Yet, for better or worse, women have been playing a hidden role in the breakneck development.

Up to three million Vietnamese died in the war, many of them male soldiers who left behind wives and young children (although women fought and died, too). When the war ended, failed collectivisation policies plunged the country into dire hardship. Single mothers supported their families with clandestine household commerce and raised their daughters to be equally resourceful. Today, female entrepreneurs own around 25% of all private enterprises in Vietnam, mostly small family outfits. Those who have reached the very top have usually overcome extraordinary obstacles to get there.

"Women? Oh, they run this country underneath it all," Frenchman Yves-Victor Liccioni, a luxury-brand PR guru and longtime resident of HCMC, tells me one evening under a canopy of fairylights at one of the city's relaxed European bistros. "They're powerful, energetic and they love making money."

It takes 40 minutes to reach Thuy Tien's home overlooking the swampy Saigon River. She lives here with her husband, two teenage children and 10 pyjama-clad housemaids. It is a typical new-money neoclassical mansion: giant gates with ornate gold metalwork, white exterior, Doric columns. In the grounds there are statues of lions standing sentry, cherubs keeping watch, and horses and dragons apparently loitering for the fun of it. There's a swimming pool, a tennis court and a garage housing three varieties of Rolls-Royce, another Bentley and an SUV. "My husband collects cars," Thuy Tien explains casually.

We go inside. It is no surprise that Thuy Tien likes gold – there is nobody in Vietnam who doesn't – but it seems unfeasible for one person to like so much of it. She designed the decor herself. Everything is so gold that it is easier to describe what isn't gold, including a white marble staircase hewn from rock from the coastal city of Da Nang. "This pure-white marble is very rare," boasts Thuy Tien. "We mined it ourselves."

Thuy Tien is married to a Vietnamese-born, Philippines-raised airline tycoon whom she met during her flight-attendant days. He is the brains behind state-owned Vietnam Airlines' international expansion, and his ties to the ruling elite have almost certainly proved helpful to his wife along the way. Nevertheless, Thuy Tien insists that her financial success is her own. "I studied every aspect of business from A to Z so I could compete at the highest level."

Relaxing on her gilded sofa, she finally opens up a little about her past. She was born in the capital Hanoi in 1970. Her father died when she was five, just before the war ended. (She won't say whether he was a soldier or which side her family was aligned with.) "My mother raised me and my five siblings alone. She was a schoolteacher and very strict. She taught us that working hard was the key to survival."

It's a lesson she says she has never forgotten, and it is true that few women in Vietnam who are hitched to wealthy men are content to be trophy wives. Shortly after she married, Thuy Tien fought for and won a lucrative contract to open Vietnam's first supermarket in 1995. "It was a joint venture with the military. I sat in meetings with all these men in uniform and they didn't believe a 25-year-old woman could handle 20,000 products. I was determined to prove them wrong." She did. The supermarket was mobbed on its opening day. "It was the first time people could do all their shopping in one place."

Thuy Tien attributes her huge success since to her knack for understanding what "modern Vietnamese consumers want". Her company is now the exclusive agent for luxury brands such as Ferragamo, Ralph Lauren, Rolex and Bulgari. "Sales are increasing every year," she says, happily. She checks her constantly buzzing iPhone before announcing, at almost 6pm, that she needs to return to the office.

No doubt due to its David and Goliath battle with the US, there is a perception that Vietnam is a tiny country. It is not that small. With almost 90m people it is the world's 13th most populous nation, and has a land area the size of Germany. Economic reform has certainly improved many people's lives – poverty has declined from 60% two decades ago to 20% today. But the wealth gap is widening and growth has stalled in the past year. Economic inefficiency, largely due to corruption inside state enterprises, including the wholesale plunder of natural resources, has caused a range of problems for ordinary Vietnamese, from inflation to high interest rates.

The government is in a dangerous bind. Increasingly unable to sustain its Communist edifice alongside runaway capitalism, it has been ruthlessly cracking down on dissent. At least 22 democracy activists and bloggers were imprisoned last year. But the super-rich are not safe, either. Tales of the wealthy quaffing champagne infused with 22ct gold, eating the brains of live monkeys as a delicacy and buying diamond-encrusted mobile phones have irritated the public. In a show of tackling corruption, the regime has recently arrested a number of top executives at state-owned enterprises for "mismanaging funds". The blood of business magnates all over the country has run cold.

Still, there is little sign of concern about this at Koh Thai, a chic restaurant serving "Thai fusion cuisine" in HCMC's business district. A lunchtime crowd of office workers is chatting noisily at tables decorated in lime green and purple. Some fashion types are smoking Menthol Slims on the balcony. Most glamorous of all is the restaurant's owner, Hana Dang. Wearing a short white dress and sky-high heels, 40-year-old Dang is busy being groomed by a make-up artist when I arrive.

If she is flustered by the curling tongs clamped to her head she doesn't show it. She tells me how much she's worth before I've sat down. "The restaurant is a new venture. I own an advertising agency with annual revenue of $50m." Her voice is sandpapery with a hint of foghorn. "I'm also a partner in a private equity firm that manages funds of $250m." With that out of the way, she flashes a charismatic smile and hands me one of her restaurant's signature cocktails, a chilli-infused strawberry vodka concoction called a Hot Lips (named after the nurse in the old TV series M*A*S*H*).

She's just as no-nonsense about her past. She was born in Hanoi in 1972 when it was "raining American bombs". Her father was enlisted with the Communist forces, the Vietnam People's Army, and was killed when she was a year old. Her mother was so traumatised that her breast milk dried up. "She fed me on water mixed with sugar. But look at me – I turned out OK, didn't I?" She lets out a raucous laugh. "If I'd been fed on milk I'd have been a supermodel." In her teens, Dang fainted from hunger in the street due to her meagre daily diet of rice mixed with corn kernels. "For years we had no meat or fish. Everyone was poor." She became an entrepreneur from a young age. "I set up a coffee stand outside our house when I was 14, and made clothes to sell. I learned a lot from those days." Most of all, she says, she learned she never wanted to be poor again. She worked hard at school and graduated from college as a fluent English speaker.

In early 1994, shortly before the US trade embargo was lifted, Dang was hired by global advertising agency McCann Erickson to work on campaigns for the first western products to arrive in postwar Vietnam: Coca-Cola, Maybelline lipstick, Nestlé milk. "It was so exciting, so much fun." She soon set up her own agency, Golden Communication Group, to take advantage of the country's insatiable new appetite for consumerism. "It was hard at the start because Vietnam is so sexist. Male clients often assumed I was the secretary, not the CEO." She pauses for effect. "They don't make that mistake any more."

Partly due to the endeavours of people like Dang, Vietnam's city centres are unrecognisable from even a decade ago. Ho Chi Minh City is full of women carrying It bags and doing valiant battle with the uneven pavements in £400 Jimmy Choos. Fake goods are increasingly déclassé. Fake noses and eyelids, on the other hand, are all the rage. Predictably, cosmetic surgery has been taking off among both sexes as Vietnamese society has grown more image conscious. PR consultant Yves-Victor Liccioni divulges that most people fly to Thailand or Singapore for big operations, while top French dermatologists fly in to Vietnam to hold "Botox bootcamps". "They come here for three weeks at a time and do nonstop injections and treatments. It's very lucrative."

Dang admits she's had "a few injections". But she insists she has no time for the conspicuous consumption of other home-grown multimillionaires. "I'm a practical person. I like what I like." She illustrates her point by noting that her zebra-striped silk jacket is from Zara. Recently divorced after a brief marriage, she's proud of her wealth, but realises it's too easy to get carried away. "It's been like a huge gold rush here. There's a lot of greed and there are still too many poor people in Vietnam." Turning 40, she says, has prompted her to focus on things she truly enjoys, like her new restaurant business, and also "to get into some charity activities" – philanthropy being as far as any of the newly rich are prepared to go when it comes to modern-day wealth redistribution.

Dang's good friend and fellow female dynamo, Alan Duong, is similarly grounded in her own way. I meet her for coffee in the ritzy Park Hyatt Hotel. Duong, 38, is the owner of a company selling modern furniture and interior design products. With so much emphasis on "aspirational lifestyles", her business has boomed. But Duong says she feels that many female entrepreneurs are slightly less enslaved than men by the desire for limitless riches. "It's fine to have a fast car, but there are other things in life. Many women don't want their children to grow up to be spoiled brats," says the mother of a one-year-old son.

When Duong was 10, her rambling French colonial family home in the centre of Hanoi was confiscated by the government. "They accused us of being capitalists because we had a big house. We were thrown on to the streets." Four years later, in 1988, their situation was so unbearable that Duong and her father, a former Vietnam People's Army soldier, joined the ranks of so-called boat people trying their luck at a better life elsewhere. "We paid a fortune for places on a fishing boat to sail to Hong Kong. The boat's capacity was 20 people and there were 72 of us packed on board. We didn't know if we'd live or die." Storms and piracy were terrifying hazards: a boat that left at the same time as theirs didn't make it, Duong says. Her mother, who had stayed behind to protect what little they still owned in Vietnam, barely slept for the entire 17 days they were at sea until she learned they were safe.

Still, they arrived in Hong Kong too late. Official resettlement programmes for Vietnamese refugees had already ended. Duong and her father spent the next five years there living in limbo in a barbed-wire compound. "It was like a prison," she says. "There was no privacy, and at shower time we were hosed down with disinfectant like pigs." Unable to prove they were political asylum seekers, they eventually returned to Vietnam when she was 19.

Almost two decades later, Duong is elated with the way her life has turned out in her home country. "Even in my dreams I didn't imagine that I would have this much money." But she's not certain that the good fortune will continue in the volatile domestic climate. Nor is she convinced that Vietnam's current population – two-thirds of whom were born after the war ended in 1975 – understands that material wealth can be fleeting.

"I'm from the generation that knows what it's like to have both nothing and everything," she says. "I don't take anything for granted."