https://localhost.com/?product_cat=demo&post_type=product&s=tukhoa

<form action="<?=home_url(); ?>/" class="col-12 p-0 pl-2" method="get" accept-charset="utf-8" autocomplete="off" >
    <div class="input-group input-group-search">
        <div class="input-group-prepend input-group-prepend-template">
            <?php 
            wp_dropdown_categories(array(
                            'name'=>'product_cat',
                            'class'=>'select-tax-search d-inline-block border-0 rounded-0',
                            'taxonomy' => 'product_cat',
                            'value_field'='slug'
                        ));
            ?>
        </div>
        <input type="hidden" name="post_type" value="product" />
        <input type="text" class="form-control border-0 shadow-none input-seach" aria-label="Text input with dropdown button" name="s" placeholder="Tìm tất cả thương hiệu , sản phẩm bạn muốn">
<button type="submit" class="btn btn-default btn-button-search shadow-none rounded-0 p-0 pl-4 pr-4" name="submit" value="submit"><svg width="20" height="22" viewBox="0 0 1792 1792" fill="#FFF" xmlns="http://www.w3.org/2000/svg"><path d="M1216 832q0-185-131.5-316.5t-316.5-131.5-316.5 131.5-131.5 316.5 131.5 316.5 316.5 131.5 316.5-131.5 131.5-316.5zm512 832q0 52-38 90t-90 38q-54 0-90-38l-343-342q-179 124-399 124-143 0-273.5-55.5t-225-150-150-225-55.5-273.5 55.5-273.5 150-225 225-150 273.5-55.5 273.5 55.5 225 150 150 225 55.5 273.5q0 220-124 399l343 343q37 37 37 90z"></path></svg></button>
    </div>
</form>