Drupal 8 Commerce Module Hook_Theme()
Try implementing hook_theme_registry_alter() and see how that goes.

function mymodule_theme_registry_alter(&amp;$theme_registry) {
    $theme_registry['commerce_product__full']['path'] = drupal_get_path('module', 'mymodule') . '/templates';
}


Your module presumably will have a folder named templates. And inside the folder you have a file called commerce-product--full.html.twig