It depends on what type of cat he is? If he is Siamese or part Siamese, they get very talkative. It is their nature. I can understand your frustration fully, because I have been there many times. You need to take apart your cat's life mentally (if this is a new behavior)? First, be sure the cat is healthy, there are no litter pan accidents, he is eating fine, playing fine, drinking enough water. Is there something lately that has changed within the home? Anything really will set a cat off it it deviates from their routine. I had one cat long ago that every time I changed the bed covers (from summer, to spring, to winter) she would start acting out at night. Wandering around the bedroom, softly mewing. Of course I rushed her to the vet put her under unpleasant observation and testings and she was fine. After sitting down and writing about her behavior, I finally figured it out, she missed the old bedcover. I took it out of storage and put it on the bed and she was happy. No more talking.
So you sort of become your own detective. Changes, no matter how minor can disrupt a cat to the extreme, or even just in subtle ways.