বাংলা টিউটোরিয়ালঃ http://obiplabon.im/734/how-to-setup-product-type-options-default-in-woocommerce/

wc-product-type-options.php

<?php
add_filter( 'product_type_options', 'op_set_product_type_options_default' );

/**
 * Set virtual and downloadable checkbox to checked
 * @param  array $options Checkbox options
 * @return array          Updated options
 */
function op_set_product_type_options_default( $options ) {
    $options['virtual']['default'] = 'yes';
    $options['downloadable']['default'] = 'yes';

    return $options;
}