Warfare and Depopulation of the Trans-Mekong Basincampaigns were an important part of the mission to build up a new
and strong kingdom in the Chao Phraya Basin in the post-Ayudhyan
period. Forced resettlement was the major objective and integral part of
Siamese warfare against its neighbours along the Mekong River Basin.
The campaigns were accompanied by mobilized armed forces, whose
duties were to administer the relocation of population and to subdue
those who escaped or resisted the relocation. People were uprooted
from their homeland and/or families and became war slaves in their new
homes. In other words, it could be said that forced resettlement was a
kind of warfare.
Moreover, the eastward expansion did not only facilitate a concen-
tration of economic and military resources for rebuilding Siamese state
power after 1767; the depopulation campaigns often involved territo-
rial consolidation of peripheral regions and distant principalities across
the Mekong River. According to Keyes, the Siamese administration in
the seventeenth century could only vaguely incorporate the region as
far as Khorat (Nakhon Ratchasima).^69 The Cambodian and Laotian
kingdoms sent tribute to the Ayudhyan court on an irregular basis. But
from the Thonburi period and particularly by the reign of Rama III of
the Chakri Dynasty, Siamese hegemony was more firmly established as
far as the east bank of the Mekong River. After the Chao Anu revolt in
1827–28, the Lao kingdoms of Vientiane and Champassak were placed
under direct Siamese administration. Battambang and Siemreap became
part of the Siamese administrative system. Tribute and local tax collec-
tion were conveyed to Bangkok annually; censuses were taken more
regularly.^70 Such dramatic development indicates a process of political
and economic centralization in mainland Southeast Asia. Only when the
new idea of a modern nation-state with strictly demarcated boundaries
and contiguous sovereignty arrived in the mid-nineteenth century, was
Siam pressured to give up her sovereignty over people and resources on
the other side of the Mekong River.^71 In other words, before the arrival
- Charles Keyes, Isan: Regionalism in Northeast Thailand (Ithaca, Southeast Asia
Program Cornell University, 1967): 7–9. - For details of the relations of war, trade and tax collection, see Puangthong, “Siam
and the Contest for Control of the Trans-Mekong Trading Networks from the Late
Eighteenth to the Mid-Nineteenth Centuries.” - Thongchai Winichakul, Siam Mapped: A History of the Geobody of Siam (Honolulu,
The University of Hawai’i Press, 1994).