Single Post Type Template http://wpsites.net/wordpress-tips/load-single-template-from-plugin-for-different-post-types/

functions.php

add_filter( 'single_template', 'wpsites_single_post_type_template' );
function wpsites_single_post_type_template($single_template) {
     global $post;

     if ($post->post_type == 'post' ) {
          $single_template = dirname( __FILE__ ) . '/single.php';
     }
     return $single_template;
     
}