Lop Yuen (Thai Standing Fish Trap) — an Upright Bamboo Lop with a Full-Height Side Door, its Slats Folded Inward, Catching Fish Swimming Upstream

"The lop yuen is a cylinder cut square at both ends. Along one side is a door running from the top down to the bottom as the entrance, made of slats tied close together like the side and then folded inward, so the fish slip and squeeze their way inside." (Sirindhorn Anthropology Centre, author ทำนุ วรธงไชย (Thamnu Worathongchai), CC BY 4.0)

Split bamboo into slats and tie them close together, almost touching, on hoops as for the lying lop, making a cylinder cut square at both ends. Size it to the water where it will be set.

Along one side make a door as the entrance, running from the top down to the bottom. Tie slats close together like the side, then fold them inward so the entrance is narrow. Some traps have a nga wai: cords tie the slats so they cross around the door from top to bottom.

Make the exit at the top, closed with a wooden latch (mai khat), so it can be opened to pour out the fish.

Photos of a real lop yuen from the Nong Bua Khok Folk Museum (Sirindhorn Anthropology Centre, author ทำนุ วรธงไชย (Thamnu Worathongchai), CC BY 4.0).

Stand the lop yuen across the flow in the drainage gaps between the paddy bunds, with the side opposite the door facing the current, to catch fish feeding upstream. At the edge of a stream or pond, set them a fair distance apart and use a fence (fueak) to guide the fish along it into the trap.

The name varies: some areas say sai nang, lop tang or lop yuen, after how it is set. In shape and method it is closer to the lop than to the sai. With slats almost touching and a narrow entrance, it catches gourami, climbing perch, walking catfish and young snakehead. Small ones are less common than the lying lop. Beware of spined fish when pouring out the catch. Source: Sirindhorn Anthropology Centre, Traditional Objects of Everyday Use database, "ลอบยืน", author ทำนุ วรธงไชย (Thamnu Worathongchai), Nong Bua Khok Folk Museum, Buriram (CC BY 4.0 licence). **Limits** The source gives no size, slat count or hoop count.