Change order status to on-hold immediately after payment

functions.php

<?php
/* 
 * Change payment status straight to on-hold after successful payment
 * 
 * By using this hook instead of 'woocommerce_thankyou' you intercept the order status change before emails are sent. 
 * By doing it this way the only email that will be sent to the customer is the one for an on-hold order.
 */

add_filter('woocommerce_payment_complete_order_status', 'semper_woocommerce_payment_complete_order_status', 10, 2 );
function semper_woocommerce_payment_complete_order_status( $order_status, $order_id ) {
	if ( ! $order_id ) {
	return;
	}
	if ($order_status == 'processing') {
	$order_status = 'on-hold';
}
return $order_status;
}