<p>Iron is something of a dichotomy in late prehistoric/early historic Mainland Southeast Asian studies. It is widely considered a substance capable of catalysing major changes in social complexity. Conversely, iron artefacts are rarely subjected to significant archaeological analysis and are generally assumed to be low value products available locally. In this paper we conduct full archaeometallurgical analysis to ancient primary iron production assemblages from Ban Kruat, Buriram Province, northeast Thailand. The attested iron production took place in a locality with extensive laterite deposits, long thought to be a source of iron. Archaeometric analysis of production remains indicates the strong likelihood that laterites were smelted to iron metal, using recipes and processes that seem to have varied little over centuries. However, as opposed to being the simple exploitation of immediately available resources, the Ban Kruat laterites were considerably richer in iron than the regional average and, furthermore, the direct bloomery reduction process employed by Ban Kruat smelters was being operated at its technical limits. To win iron from a marginal ore, the furnaces were necessarily run very hot and very reducing, which runs the risk of producing unusable cast iron, consumes vast quantities of fuel, and requires a huge labour input. Ban Kruat iron was anything but ‘cheap’. We propose that better/richer ore sources within 100–200&#xa0;km were inaccessible, but such was the value of this strategic material, local populations would fulfil their iron needs at almost any cost.</p>