Custom WooCommerce Lazy Load Product Thumbnail display.

theme-functions.php

function woocommerce_template_loop_product_thumbnail() {
  $image_src = wp_get_attachment_image_src( get_post_thumbnail_id(),'full' );
    echo '<img data-original="' . $image_src[0] . '" width="400" height="900" class="attachment-shop_catalog wp-post-image lazy"><noscript><img src="' . $image_src[0] . '" width="400" height="900" class="attachment-shop_catalog wp-post-image lazy"></noscript>';
}