Marvel's president of production Kevin Feige recently said that a sequel to the mythological action film is already planned.
Speaking to Entertainment Weekly, Branagh said: "I am not sure I am done with Thor's universe, or if it is done with me."
The helmer also denied that he had saved up any ideas for a second film.
He added: "You can think of stuff for two or three later, if you get the chance to do them. But you won't if one isn't good enough."
Thor is the director's 14th film, following on from his 2007 psychological drama Sleuth.
Watch a trailer for Thor below: