If Thailand opened the dam, there wouldn't be an issue. Right now, the ones that are left in the wild, which is less than 10% of the original population, cannot swim to another part of the river. This makes them easy to be caught since they remain in a relatively small area. If they can swim out, they can potentially breed and repopulate. Of course, this mean Thailand has to care, which they don't. I believe there is a way to breed to them, but it becomes increasingly harder when you can't sex them. You would obviously need a decent amount of money, knowledge and a significant body of water.