En el function.php

reordenar.php

<?php

add_filter( "woocommerce_checkout_fields", "reordering_checkout_fields", 15, 1 );
function reordering_checkout_fields( $fields ) {

    ## ---- 1. REORDERING BILLING FIELDS ---- ##

    // Set the order of the fields
    $billing_order = array(
    	'billing_rut',
        'billing_first_name',
        'billing_last_name',
        'billing_email',
        'billing_phone',
        'billing_company',
        'billing_country',                
        'billing_address_1',
        'billing_address_2',
        'billing_postcode',        
        'billing_state',
        'billing_city'
    );

    $count = 0;
    $priority = 10;

    // Updating the 'priority' argument
    foreach($billing_order as $field_name){
        $count++;
        $fields['billing'][$field_name]['priority'] = $count * $priority;
    }

    ## ---- 2. CHANGING SOME CLASSES FOR BILLING FIELDS ---- ##
    $fields['billing']['billing_rut']['class'] = array('form-row-wide');

    $fields['billing']['billing_email']['class'] = array('form-row-first');
    $fields['billing']['billing_phone']['class'] = array('form-row-last');

    $fields['billing']['billing_state']['class'] = array('form-row-first');
    $fields['billing']['billing_city']['class'] = array('form-row-last');

    ## ---- RETURN THE BILLING FIELDS CUSTOMIZED ---- ##

    return $fields;
}

Y en en tmp-somela/woocommerce/checkout/form-billing.php

<script> $ = jQuery; $( window ).load(function() { $("#billing_address_1_field").insertAfter("#billing_postcode_field"); $("#billing_address_2_field").insertAfter("#billing_address_1_field"); }); </script>