The naga (นาค; Pali nāga) is the great water-serpent of Southeast Asian cosmology — guardian of rivers, rain and the underworld treasure, and, in the Buddhist frame, a devout half-divine being who shelters the meditating Buddha under its hood. In the Lanna world the naga is everywhere at once: carved along temple stair-rails, coiled in the founding-myths of cities, invoked in rain-making and protective magic, and — as the catalogue shows — narrated at length in the birth-story literature.
Eight witnesses carry a naga name in their title — every one of them a jātaka / watthu narrative (the Mahānāga-type and Bhūridatta-type serpent-king tales), not a ritual or cosmological treatise.
Inference — this is a sharp and telling shape. The naga the catalogue attests so far is the naga of story — the serpent-king as a moral character in a birth-tale — and not the naga of wichaa: the serpent invoked in a rain rite, drawn into a yantra, or laid out as the naga-under-the-earth whose direction a house-builder or grave-digger must consult. Those functional nagas almost certainly sit inside manuscripts that are titled for their genre (a ritual manual, an almanac) rather than for the serpent — so a title search undercounts the naga badly. Reading `raw_metadata` and page-content, not just title lines, is how the rest would surface.
Tradition — the following is background from the wider Thai–Lanna tradition, not drawn from these eight manuscripts; treat specifics as orienting, not authoritative.