Change product tag on stock change in WooCommerce

functions.php

function action_woocommerce_low_stock( $wc_get_product ) {    
    // Product set tag id(s), multiple IDs can be added, separated by a comma
    $wc_get_product->set_tag_ids( array( 'YOUR TAG ID' ) );

    // OPTIONAL: Set category ids
    //$wc_get_product->set_category_ids( array( 39, 2 ) );

    // Save
    $wc_get_product->save();
}
add_action( 'woocommerce_low_stock', 'action_woocommerce_low_stock', 10, 1 ); 

https://stackoverflow.com/questions/76219364/automatically-change-product-tag-on-stock-change-in-woocommerce