VIENTIANE — The capital of Laos is a low-rise, low-key city, especially when compared with the hulking high-rises and bustling streets of better known Southeast Asian cities such as Bangkok, Kuala Lumpur and Singapore. But Vientiane is fast shedding its sedate reputation amid a building boom ahead of a series of international summits that will bring U.S. President Barack Obama, China’s President Xi Jinping and a host of other world leaders to the city in 2016. Construction cranes tower over the city’s two- and three-storey shophouses and hotels — the din of diggers and drills drowning out the once quiet capital’s increasingly dense traffic. “So many shopping malls now — around 20 going up all around the city,” said Pouthong Sengchanh, standing over a model of the Vientiane New World project — a mix of shops, restaurants and offices newly stretching along the city’s Mekong riverfront.