Overview
The Ly were Vietnam’s first durable dynasty, and one of the things a durable dynasty does is regulate dress. Court costume was codified on Chinese models, as it was in every state in the Sinitic orbit, while ordinary clothing stayed adapted to a hot, wet, rice-growing country. The gap between the two was wide and stayed wide.
Key garments and style
Kings and officials wore cross-collar robes closing to the right, with rank shown by colour, by pattern and by the form of the headwear. Ly Vietnam also legislated in the other direction: court records note restrictions reserving certain colours and materials to the throne, which is how dress regulation usually appears in the sources — as a prohibition on everyone else.
Everyday dress was different in kind. It was short, unlined and often little more than a wrapped lower garment for men working in water, with women in a simple skirt and a breast-cloth; going barefoot was normal at every level below the court. Buddhism was the state religion under the Ly, so monastic robes were a visible and honoured part of the clothed landscape.
The evidence is mostly indirect — temple and pagoda sculpture, ceramic figures, and later texts — since no Ly garment survives.
Transition
The Tran inherited this arrangement and kept it through the Mongol invasions, and the Sinitic court robe with local dress beneath it remained the pattern of Vietnamese clothing until the Nguyen reforms recut it.