retired said..
I would use marine ply.
If you can find good marine ply, go for it but a lot of readily available "marine ply" has good durable face ply's but the internal material not so good, with the A bond adhesive that marine ply should have. Would work but the edges would need to be meticulously sealed and painted.
I too would advise against merbau, the bloody stuff bleeds at the drop of a hat.