In fact the Navy could offer rides to tourists, which would pay for operation and maintenance. It could sell small models to the tourists to be used in bathtubs. Imagine owning a real replica of a Thai sub that came with torpedoes and could sink a bar of soap.
While cruising the river it could also pull Navy barges in order to reduce logistic expenses required to restock Navy bases. I am sure that most countries would think twice about invading Thai waters.
Producer Paul
Bangkok