Aeon plans more malls in Cambodian cities and operates a micro-finance firm so shoppers can buy on payment plans. Its new mall, boasting shops from the likes of Mango, Levi's and Versace, drew 100,000 visitors daily when it opened in June.
"The middle class is growing," said Aeon spokesman Satoshi Otsuka. "The average age for Cambodians is early 20s and they're fashion-conscious."
Chy Sila was born the same year the Khmer Rouge swept to power and says he lost "countless" relatives to Pol Pot's genocidal pursuit for a peasant utopia.
Today's capitalist Cambodia, with an economy that averaged 8.1 percent growth from 2000-2012 and expanded 7.4 percent last year, according to the World Bank, is a far cry from what the Khmer Rouge envisioned when it abolished money and property ownership, executed entrepreneurs and blew up the central bank.
Read MoreThe $4 million Lamborghini Veneno's maiden voyage
Forty years after the population of Phnom Penh were emptied into labor camps, the city is swelling, with malls, office towers, hotels and fast-food chains popping up rapidly.
Modern SUVs, and even the occasional Lamborghini or Porsche, cruise its once potholed streets.
The World Bank says the country of 15 million people is a top global performer in tackling poverty, having cut the ratio of poor from 53 percent of its population in 2004 to 20 percent in 2011.
Foreign direct investment has grown, from $2.65 billion recorded in 2007 to as high as $10.8 billion in subsequent years, according to Cambodia's investment board.
Read MoreAsian labor activists team up to press wage claims
There's now a small stock market and the number of banks has nearly doubled since a decade ago, with 35 commercial lenders providing $9.5 billion in loans since records started. Cambodia's Credit Bureau expects that to surpass $14 billion by 2020 and credit demand to almost double to 3.3 million people.
The average bank loan in 2004 was $3,895, about a fifth of last year's average of $19,096, according to Acleda Bank, Cambodia's biggest lender.
"Loans are good for young people like me," said Hour Veasna, 20, as he signed up for financing from Aeon to buy a $600 camera, equivalent to five months salary. "We don't have enough money to purchase things that we want."
In the first half of 2014, bank deposits grew 13 percent and loans to the private sector were up 28 percent, central bank Governor Chea Chanto said in a recent speech. Three million Cambodians use banks to deposit money, up 18 percent from last year, with about 600,000 users of credit or debit cards.
Read MoreRich and poor alike are worried about income gap
But there are still plenty of Cambodians who don't have such privileges and Chy Sila says he's saddened by the yawning gap between rich and poor. He raises money to send children to school and has cultivated an image as a humble entrepreneur, driving a Ford SUV rather than luxury cars such as Rolls-Royce, which entered the local market in June.
The new-found opulence of Phnom Penh can leave a sour taste in the mouths of those who struggle to get basic services in Cambodia, where hospitals are overwhelmed and average annual income is $950 - or $2.60 a day - nearly half that of Vietnam and a fifth of Thailand.
"Economic growth is only for the city," said rice farmer Heang Samnang, waiting with her sick daughter at the city's foreign-funded Kantha Bopha Hospital, which provides free treatment to millions of poor. "In rural areas, there's no development, we just work on farms."