You could use a radio field and dynamically load the choices of the radio field using the post_id as the value of the field and the thumbnail <img> tag as the value. https://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/
However, I don’t know what you’d do with this in elementor since the value returned would be the image ID. You might want to look at creating an acf/format_value filter (priority > 10) for this field that would take the ID and return the image URL https://www.advancedcustomfields.com/resources/acf-format_value/
