Alma 18:21 - 18:26
Alma 18:21 And now, if thou wilt tell me concerning these things, whatsoever thou desirest I will give unto thee; and if it were needed, I would guard thee with my armies; but I know that thou art more powerful than all they; nevertheless, whatsoever thou desirest of me I will grant it unto thee.
Lamoni asks Ammon to tell him about the things of the Great Spirit and in return would guard Ammon with his armies. However, Lamoni says he knows that Ammon would not need any such protection. But he would still give to him what he had if he asked for it.
Alma 18:22 Now Ammon being wise, yet harmless, he said unto Lamoni: Wilt thou hearken unto my words, if I tell thee by what power I do these things? And this is the thing that I desire of thee.
Ammon says what he desired of the king was for him to listen to him and believe what Ammon told him. Ammon knew now how to get to the king but what he would tell him would not hurt the king in anyway but of great value to him.
Alma 18:23 And the king answered him, and said: Yea, I will believe all thy words. And thus he was caught with guile.
Lamoni says that he will believe all that Ammon will tell him.
Since the king said he would give anything to Ammon and this was all Ammon asked, that is, to listen and believe him, the king was obligated to pay attention to Ammon’s words. A very wise way to entrap Lamoni, but it would not do the king any harm.
Alma 18:24 And Ammon began to speak unto him with boldness, and said unto him: Believest thou that there is a God?
Ammon thinking he had the full attention of the king began his teaching by find first trying to find out what the Lamoni believed at this point in his life. So the first question, did the king believe in God?
Alma 18:25 And he answered, and said unto him: I do not know what that meaneth.
Lamoni replied, he did not know what the question meant.
I'm guessing that the king was wondering if Ammon was referring to a single God, many gods or an idol.