Champasak Province in the context of Sekong province

Don Det (Lao: ດອນເດດ) is an island in the Mekong River in the Si Phan Don ("Four Thousand Islands") archipelago in Champasak Province of southern Laos.

Old Khmer is the oldest attested stage of the Khmer language, an Austroasiatic language historically and presently spoken across Cambodia, Southern Vietnam, and parts of Thailand and Laos. It is recorded in inscriptions dating from the early 7th century until the first few decades of the 15th century. Such inscriptions, spanning nearly a millennium and numbering well over a thousand, present one of the most extensive sources of documentation in Southeast Asia.

Old Khmer was written in an early variant of the Khmer script derived from Pallava, a southern variant of Brahmi, and in turn became the basis of the scripts used for Thai and Lao. Along with Brahmi and Indian influence on Cambodia, Old Khmer saw an influx of Sanskrit loanwords in the domains of religion, philosophy, and to a lesser extent, politics. Despite this, Old Khmer retained a prototypical Austroasiatic typology in phonology, syntax, and morphology, being sesquisyllabic, analytic, having a rich system of derivational affixes.

The Si Phan Don (Lao: ສີ່ພັນດອນ; meaning '4,000 islands') is a riverine archipelago in the Mekong River, Champasak Province in southern Laos. Si Phan Don is part of Khong District, including the islands and part of the mainland in the east. Si Phan Don is dotted with numerous islands, half of which are submerged when the Mekong River is in flood. The principal islands of Si Phan Don are Don Khong (the largest), Don Som (the second largest), Don Det and Don Khon. Si Phan Don borders Cambodia and historical and cultural ties link the people on both side of the border. Pakse is the closest of the bigger cities in Laos to the area.

Key features of the Si Phan Don archipelago include: