function default_comments_on( $data )
{
$myCustomPostType = array("my_custom_post_type_1", "my_custom_post_type_2", "contacts"); /* Custom Post Type Array */
if (in_array($data[\'post_type\'], $myCustomPostType))
{
$data[\'comment_status\'] = \'open\';
}
return $data;
}
add_filter( \'wp_insert_post_data\', \'default_comments_on\' );
Add this code in functions.php