single-mycustomposttype.php

add_filter('single_template', function($original){
  global $post;
  $post_name = $post->post_name;
  $post_type = $post->post_type;
  $base_name = 'single-' . $post_type . '-' . $post_name . '.php';
  $template = locate_template($base_name);
  if ($template && ! empty($template)) return $template;
  return $original;
});

single-*custom-post-type-slug*.php

<?php
    $slug = get_post_field( 'post_name', get_post() );
    $slug = ( locate_template( 'templates/*custom-post-type-slug*/' . $slug . '.php' ) ) ? $slug : 'default';

    get_template_part( 'templates/*custom-post-type-slug*/' . $slug  );
?>

themeroot
| |single-cases.php
|-templates
| --cases
|   |default.php
|   |case-one.php
|   |case-two.php

<div class="container">

    <div class="row">

        <div class="col-md-9">
            <div class="panel panel-default text-center">
                <?php $loop = new WP_Query( array( 'post_type' => 'items', 'posts_per_page' => 5 ) ); ?>

                        <?php while ( $loop->have_posts() ) : $loop->the_post(); ?>
                            <?php the_title();?>
                            <?php if(has_post_thumbnail() ) { the_post_thumbnail(); } ?>
                            <?php the_content();?>
                        <?php endwhile; ?>

                <?php wp_reset_query(); ?>
            </div>
        </div>

    </div>

</div>

<?php
/*
Template Name: Full-width page layout
Template Post Type: post, page, product
*/