OUDOM XAI, Laos — Wang Quan, the new Chinese owner of a hotel in this farm town in the tropical mountains of northern Laos, is hoping that the first of 20,000 Chinese workers will arrive soon to start construction on a new railroad.

The Chinese-financed railway is to snake its way through dozens of tunnels and bridges, eventually linking southern China to Bangkok, the capital of Thailand, and then on to the Bay of Bengal in Myanmar, significantly expanding China’s already enormous trade with Southeast Asia.