The administrative reforms in Siam around the turn of the twentieth century are probably one of the most studied topics in the history of Thailand. Known as the Chakri reforms, it is usually described as the period when the royal elite worked to create a Siamese nation-state under the guidance of the absolute monarchy. This transformation encompassed both territorial integration and administrative centralization. This article offers a new perspective on this transformative period through an analysis of changing documentary and spatial practices in Siam from the mid-nineteenth to the early twentieth century as one of the most crucial intrinsic dynamics of state formation. The emphasis is on the mundane practices of documentation – among other spatial-material practices and processes – that produce the effect that the state exists. We show how this new paper regime articulated a standardisation of written official documents, the birth of the file as a technology to deal with the avalanche of documents circulating between sections of the burgeoning administration, and the spatial organisation that created the office – fields where officials produced and stored documents according to specific regulations. We exemplify this new regime of documentary practices in Bangkok and beyond, with special reference to the paper and spatial works of the provincial gendarmerie.