This episode benefited from a couple of ringers: the story was by Borden Chase, who wrote or co-wrote such classic westerns as "Red River" and "Winchester '73," while the director, Andrew McLaglen, directed many of John Wayne's later films.
As was typical of the all-Asians-are-alike mentality of the era, Umeki, who is Japanese, was cast as a Chinese.
As was typical at the time to cast anyone for anyone: whites as Asians, Italians as indians, old as young, gay as straight, etc., Umeki- like all actors who need employment no matter their true histories- likely had no problem saying "I am Chinese..." for the camera.
Sheriff Marden's wife is played by Phyllis Coates, who also played Lois Lane in the first season of "The Adventures of Superman".