I'd take a wild guess that Tyhm wrote those. I never really knew Tyhm, but there was this one quest people called Tyhm's quest, which had a Riddle Bridge that clearly referenced Monty Python. Because it was called Tyhm's quest is certainly a reason to believe it was made by Tyhm, and because that referenced Monty Python, it would make sense to believe those swamp town books were written by him.