reorder-shipping-method.php

/*
This code snippet reorders the shipping methods in your WooCommerce website,
in an ascending order in terms of shipping costs. 

Copy the content to your theme's functions.php file or use a custom code snippet plugin
like this one: https://github.com/woocommerce/theme-customisations to prevent the code 
from being overwritten during theme updates.
*/
add_filter( 'woocommerce_package_rates' , 'reorder_shipping_methods', 10, 2 );
function reorder_shipping_methods( $rates, $package ) {
	//  if there are no rates don't do anything
	if ( ! $rates ) {
		return;
	}
	
	// get an array of prices
	$prices = array();
	foreach( $rates as $rate ) {
		$prices[] = $rate->cost;
	}
	
	// use the prices to sort the rates
	array_multisort( $prices, $rates );
	
	// return the rates
	return $rates;
}