There are only few people who can do multiple professions like writing and direction are very closely attached but a writer can be a director is proved by Trivikram and Koratala Siva.
This may not be successful for every writer as Vijayendra Prasad who penned for many blockbuster hits like Baahubali and Bajrangi Bhaijaan also tried his luck at direction for three times and failed disastrously at the box office. So he decided that he will only try his hand in scripting rather than directing.