Aaron, Omner, and Himni present themselves to Lamoni’s father using the same offer that Ammon had. They offer to be servants. The overking is beyond that. He had already had an encounter with Aaron that left him with questions, and the overking left Aaron with the request that Ammon visit him in the land of Nephi. Ammon wasn’t there, but the overking hopes that Ammon’s brothers might be similar to Ammon.
The king has questions. When the story was given of Ammon’s meeting and conflict with Lamoni’s father on the road to Middoni, we were told that Lamoni had told his father “all the cause of his tarrying in his own kingdom, that he did not go unto his father to the feast which he had prepared” (Alma 20:12). Few details of what he said were recorded at that time, but the story must have included some of Ammon’s teachings, for Lamoni’s father poses questions that he indicates came from Ammon’s teaching. Specifically, the overking does not understand the Spirit’s ability to communicate with Ammon, and he does not understand the principle of repentance.
This last sentence should be interpreted. It certainly was not true that Lamoni’s father would not understand that someone might do something wrong and be sorry for it, and then change. That part of repentance is human and universal. What he did not understand was the role of the coming Messiah in creating the conditions whereupon repentance could enact a removal of the stain of sin and could create the condition that would allow one to not be “cast off at the last day.”