Even with his hunting weapons, a solitary Ammon would hardly be a threat to the Lamanites. Additionally, we are not told how it was that they recognized Ammon as a Nephite. It is quite possible that it was because of the manner of dress, since there are, even today, certain unique styles and patterns of dress among the Maya of Guatemala that allow one who knows the code to determine the local of the persons origin by the designs and colors in certain items of clothing.
What we have in this description is a very clear indication that Ammon is being treated as a captive. This is significant in a Mesoamerican context because of the religious and political importance of captives to the public functioning of the city state. Such captives were always bound. It may also be significant that he was "carried" before the king, rather than being allowed to walk. This type of description indicates the public humiliation of the captive, and reflects the utter domination of the captor over the captive. This was an important part of captive display rituals among the Maya.
Next, we notice the range of options that was open to the king regarding this prisoner. This is a captive from a foreign polity, and one who has done nothing against the Lamanites except enter their land. Thus this is a man with no crime except being a foreigner. Nevertheless, the options of the local king include permanent captive, or death. This range of options also fits what is known of the way that captives were treated. While Ammon was certainly not captured in war, he was nevertheless presented as a captive of war, and his fate was possibly the same as a captive of war.