Tea chests were made with plywood that was 1/4 inch thick or less. The bottom was removed because that was really the top and it was removed to get the tea out. They were bound with tin (tin plated sheet steel). The inside corners were braced with lumber about 1" X 1". You might find that Louan ply would be too soft to resonate well. How about birch? Or maybe even a doorskin would do but that might need bracing, which would add more complexity than it is worth.