Want to change the position of the email and phone field of the billing address at the top of the checkout form? No problem.

With a few lines of code, you can change the order of WooCommerce checkout fields and create a seamless flow. See the following code example.

function custom_checkout_fields_order($fields) {
    // change the email and phone field position at top
    $fields['billing']['billing_email']['priority'] = 5;
    $fields['billing']['billing_phone']['priority'] = 6;

    return $fields;
}

add_filter('woocommerce_checkout_fields', 'custom_checkout_fields_order');

There are more scenarios and examples you can check here https://yourblogcoach.com/change-the-order-of-checkout-fields-in-woocommerce/