The beginning of the discussion with Lamoni’s father is essentially the same as the beginning of Ammon’s discussion with Lamoni. The lesson begins with the question: “Believest thou that there is a God?” See Alma 18:24 for Ammon’s very similar question to Lamoni.
There is an interesting side note to the story of the overking’s conversion. The overking’s answer is different from Lamoni’s. Where Lamoni had not believed in God, but in a Great Spirit, his father understands that there is a god named Jehovah. The issue is not a belief in any divine being, but rather in a specific one. Ammon and Aaron asked if they believed in Jehovah. Lamoni was unfamiliar with Jehovah. Lamoni’s father is familiar with Jehovah, because Jehovah was the God of the Amalekites. They, and the followers of the priests of Noah, followed the Order of the Nehors, which did believe that Jehovah was their God. Thus, Lamoni’s father had familiarity because he had allowed the Amalekites to have their own form of worship.
This tells us that even though there might have been some Lamanites who remembered something of the law of Moses, it was not the most common religion in the land. It was apostate Nephites, not the typical Lamanite, who believed in Jehovah.
The very last sentence is critical to the story. While Lamoni’s father does not believe in Jehovah, he is willing to accept that He exists. At this point, however, it does not mean that the overking accepts Jehovah as the sole God, but rather that He is a god among many. That change is yet to come. At this point, it is a willingness to believe that is important.