The district was created on 1 April 1992 by splitting off the five western
tambons of
Tha Mai district. It was upgraded to a full district on 5 December 1996. Its name "Na Yai Am" directly translates as "grandma Am's
rice field". This refers to the residence and rice field here in the past of an old woman named Yai Am (grandma Am) and a place where people passed by. Therefore, it was called by name of the owner. ==Geography==