While he worked with Tamil actor R. Madhavan in "Tanu Weds Manu", he roped in Dhanush for "Raanjhanaa".
"I think it's because the scripts I write require characters with lot of simplicity and honesty. I find that in southern actors and that's precisely why I work with them," Rai told.
He will be teaming up with Dhanush for another Hindi project in 2014.
"I don't write (stories) keeping any of these actors in mind, but they somehow are apt for the characters in my stories," he said and added that he has "developed" another "script" for Dhanush.
In "Raanjhanaa", releasing Friday, Dhanush plays a Hindu boy in love with a Muslim girl, essayed by Sonam Kapoor.
It is produced by Eros International, and also features Abhay Deol, Swara Bhaskar and Mohammed Zeeshan Ayyub in important roles.