Wordpress custom thankyou page by order total

i want echo a custom message for each order total value in thankyou.php

exemple:

i try

<?php $order->get_total();
    if ($order == '59.9') {
        echo 'custom 1';
    }
    else if ($order == '159.8') {
    echo 'custom 2';
    }
    ?>

why doesn't work?