<?php
        if (is_single()) {
            while (have_posts()) : the_post();
                // get thumbnail
                wikiwp_get_thumbnail($post);
        ?>
<div>This should stay here in a post</div>
<div>And this should also be visible in this case</div>


       <?php
            endwhile;
        } else {

        ?>

<div>This should stay here in a page</div>

        <?php
        }
        ?>

<?php
                if (is_page()) {
                    while (have_posts()) : the_post();
                        // get thumbnail
                        wikiwp_get_thumbnail($post);
                ?>

<?php
                endwhile;
            } else {

            ?>

[thumbnail]
This should stay here
And this should also be visible in this case

[thumbnail]
This should stay here on a page