WordPress is also provide more filters to change custom queries.
https://codex.wordpress.org/Custom_Queries
add_filter('posts_join', 'custom_query_join' );
$premium = new WP_Query( $premium_args);
remove_filter('posts_join', 'custom_query_join' ); // remove filter bcz not effect to another query to use after this query.
function custom_query_join( $join ){
$join .= 'Put here join to table';
return $join;
}