I'd suggest you to speak with psychiatrists/psychologists/experts about it, or maybe research a little bit and then post your question on Psychology & Neuroscience.
I have problems with sleeping since I have been working on projects that have so much to do with thinking, and have seen many colleagues of mine with similar not-sleeping-well problems, yet we are adults. In my case, it wasn't a problem when I was a child. Since our jobs are related to so much thinking, we just don't sleep well and sometimes we are sleep-working, which means we are not really at full-sleep and as we are at semi-sleep stage, we are solving an "algorithm" or "equation".
I suspect that your son may seem to be also a young thinker of some sorts, since he reflects on "talking" and "singing". I would not worry about it much, but I would not try to control it too much either.
You can pay attention to see if during the day, he thinks much. If thinking might be a case for your son, you can try to make him active to do actions so that he becomes tried, and he will go to sleep. Sports and plays with other friends might be a good idea and letting him to be alone or play alone may not be.
Overall, this may be best addressed speaking to professionals.