These days, Thu Huong no longer shops at the fresh produce market near her home, opting instead to hop in a taxi and head off to Aeon Co.'s 9-month-old mall in Hanoi. There, as she shops for her family of five, she can bask in the air-conditioning and enjoy free Wi-Fi.

"It's very convenient to shop there, I can buy all the different things that my family needs for a whole week. I also feel more modern and fancy when shopping in a place like this," said the 30-year-old dairy company employee.

With a young population, an expanding middle class and one of Southeast Asia's fastest-growing economies, Vietnam is an alluring market for Aeon, Takashimaya Co. and Seven & I Holdings Co. The reason: China is slowing and growth is flat-lining at home.