display_select_featured.php

<?php 
add_action( 'genesis_entry_header', 'featured_post_image', 8 );
/**
 * Conditionally add the post thumbnail to single post
 */
function featured_post_image()  {
	
	if ( ! is_singular( 'post' ) )
		return;
	
	if( ! function_exists( 'get_field' ) )
		return;
	
	if ( get_field( 'show_image_single' ) ) {
		the_post_thumbnail( 'post-image' );
	}
	
}