Retrieve comments from current post using SQL

Send your post id in the function and it will look something like this

<?php
 function dp_recent_comments_ajax($ID) {
    $no_comments = 5;
    $comment_len = 300;
    global $wpdb;

$request = "SELECT * FROM $wpdb->comments";
$request .= " JOIN $wpdb->posts ON ID = comment_post_ID";
$request .= " WHERE comment_approved = '1' AND post_status="publish" AND post_password =''";
$request .= " AND ID='{$ID}' ";
$request .= " ORDER BY comment_date DESC LIMIT $no_comments";