Wanderlust World Wanderlust World The relationship between Laos and Thailand is complex, rooted in centuries of shifting borders, suzerainty, and colonial intervention. The short answer is no—Laos was never fully incorporated as a province or integral part of the Thai state. However, for nearly a century, it existed as a vassal state under Siamese (Thai) influence.
Following the collapse of the Lan Xang kingdom, the Lao principalities (Luang Prabang, Vientiane, and Champasak) fell under the sway of the Siamese Kingdom. In 1779, Siamese forces under General Taksin captured Vientiane, bringing the Lao kingdoms into the Siamese tributary system. This meant the Lao rulers paid tribute, provided labor and military levies, and acknowledged the Siamese king as overlord, but retained internal autonomy over local administration, culture, and religion.
The dynamic shifted dramatically with the arrival of French imperial ambitions in Indochina. Following the Franco-Siamese War of 1893, Siam was forced to cede all territories east of the Mekong River to France. This established the French Protectorate of Laos, effectively severing the political ties to Bangkok. The Mekong became a hard border, dividing Lao-speaking populations—a division that persists today between Laos and Thailand's northeastern Isan region.
Laos remained under French rule until 1949 (within the French Union) and gained full independence in 1953. Today, Laos and Thailand are sovereign neighbors with deep cultural, linguistic, and economic ties. The "Lost Territories" narrative remains a sensitive historical topic in Thailand, but the two nations cooperate closely within ASEAN.