To create WooCommerce custom thank you page Please follow this steps:

Login to your WordPress website and navigate to Appearance

Locate file: functions.php

Add Following code and change custom links to yours:

// Redirect custom thank you
 
add_action( 'woocommerce_thankyou', 'bbloomer_redirectcustom');
 
function bbloomer_redirectcustom( $order_id ){
    $order = new WC_Order( $order_id );
 
    $url = 'http://www.lexen.net/custom-link/';
 
    if ( $order->status != 'failed' ) {
        wp_redirect($url);
        exit;
    }
}