Mueang Roi Et Municipality Aquarium

The Mueang Roi Et Municipality Aquarium sits at the edge of Bueng Phlan Chai, the large lake that anchors Roi Et town, and it’s free every day it’s open — Tuesday through Sunday, 08:30 to 16:30. Run by the municipality rather than a private operator, it’s built around two connected buildings: the first holds a hall, lecture rooms, an exhibition space, and the ticket counter (no charge, but you still queue through it); the second is where the fish are.

That second building is the reason to come. Twenty-four smaller tanks display native freshwater species drawn from three of Thailand’s major river systems — the Mekong, the Chao Phraya, and the Mun — schooling fish, catfish, and other species you won’t find labelled in English at most aquariums this size. The centrepiece is a single large tank measuring 8 by 16 metres and holding around 400 cubic metres of water, with a walk-through tunnel running underneath it. Standing in the tunnel puts fish above and to every side of you at once, which is the one moment here that outclasses a lot of pricier aquariums elsewhere in Thailand.

Signage leans Thai-only in most sections, so this rewards visitors happy to look rather than read — feeding times draw a small crowd of local families, and the compact scale means you’re done in well under an hour without feeling rushed through.

Insider Tip: Combine the visit with a walk around Bueng Phlan Chai itself — the lake’s public park, with its own small night market some evenings, makes the aquarium a 20-minute stop within a longer afternoon rather than a standalone destination.

Watch out: It’s closed Monday as well as public holidays — plan a Tuesday-to-Sunday visit or you’ll find the gate shut.

Roi Et gets little international tourism compared to Isan’s bigger draws like Khon Kaen or Khorat, so outside a Thai school trip you’ll likely have the tunnel to yourself. Bring a camera — the underwater tunnel shot is the one worth taking home.

Pair it with a loop around Bueng Phlan Chai itself, or the nearby Roi Et National Museum for a fuller half-day in Roi Et town.