In case you don’t want to search titles, content, excerpt or anything at all, only within keywords you specify for each post, it is actually possible.
There is an Ajax Search Pro custom meta box under each post on the editor screen.
If you can’t see this box, make sure it’s enabled for this post type and set to visible: Ajax Search Pro meta box on editor screen
By default the plugin looks in titles, content and excerpt as well. First you need to disable all these options on the General Options -> Sources panel. However in order for the plugin to work, at least one field must be enabled, therefore make sure that the Search in post (and CPT) IDs?option is enabled.
This step is to make sure that at least on field is enabled, otherwise the plugin might skip the search process completely.
If you don’t need Front-end filters, use Option 1
..if you use Front-end filters, but not the generic ones, then Option 2
..if you want to be able to search titles and content, then Option 3
On the post editor screen, keep adding additional keywords to the meta box (space separated), and the plugin will use those exclusively.