France's initial interest in Laos stemmed from a belief that the Mekong River would provide a backdoor route to China and the resource-rich Yunnan region. Although the Mekong Exploration Commission of 1867-1868 soon discovered that significant stretches of the river were unnavigable, enthusiasm for Laos was rekindled by explorer Auguste Pavie , who conducted a "conquest of hearts" in the name of France in the 1880s and 1890s. As vice-consul in Louang Phabang, Pavie persuaded the northern kingdom to pay tribute to France instead of Siam, and by 1893 Siam had relinquished its claim to all territory east of the Mekong River.

For half a century, Laos was ruled as a French colony , with Vientiane as their administrative capital. But the French interest was halfhearted and Laos was in reality a neglected backwater of France's other Southeast Asian acquisitions.