// REGISTER CSS & JS
add_action( 'admin_enqueue_scripts', 'acf_flexible_content_thumbnail' );
function acf_flexible_content_thumbnail() {
    
	// REGISTER ADMIN.CSS
	wp_enqueue_style( 'css-theme-admin', get_template_directory_uri() . '/css/admin.css', false, 1.0 );

	// REGISTER ADMIN.JS
	wp_register_script( 'js-theme-admin', get_template_directory_uri() . '/js/admin.js', array('jquery'), 1.0, true );	
	wp_localize_script( 'js-theme-admin', 'theme_var',
                array(
                    'upload' => get_template_directory_uri().'/img/acf-thumbnail/',
                )
	);
	wp_enqueue_script( 'js-theme-admin');
	
}