WordPress “Next Post” URL and Thumbnail

You can use get_adjacent_post function for retrieving that data. This function retrieve adjacent post. Can either be next or previous post.

For previous post

<?php

  $prevpost = get_adjacent_post( false, '', true, 'category' );

  $image = get_the_post_thumbnail( $prevpost );
  $name = get_the_title( $prevpost );
  $url = get_permalink( $prevpost );

?>

For next post

<?php

  $nextpost = get_adjacent_post( false, '', false, 'category' );

  $image = get_the_post_thumbnail( $nextpost );
  $name = get_the_title( $nextpost );
  $url = get_permalink( $nextpost );

?>