Get post thumbnail image src https://css-tricks.com/snippets/wordpress/get-featured-image-url/

thumbnail_src.php

<?php
//wp_get_attachment_image_src( $attachment_id, $size, $icon );
$featureimage = wp_get_attachment_image_src( get_post_thumbnail_id() );
$featureimage_url = $featureimage[0];
echo $featureimage_url;

// https://css-tricks.com/snippets/wordpress/get-featured-image-url/
$thumb_id = get_post_thumbnail_id();
$thumb_url_array = wp_get_attachment_image_src($thumb_id, 'thumbnail-size', true);
$thumb_url = $thumb_url_array[0];
?>