Timing isn't my strong suit ?

He's not very good at being in the right place at the right time.

No, in the context of the movie it means that his stammer makes it difficult for him to express his sense of humor or make people laugh by making witty remarks. In telling a joke, timing is important -- if the listener has to wait a long time for the punch line, it's not very funny. (although in context, his saying that was actually pretty funny.)

khoff is correct. I love that movie.

The King's diction teacher, Mr. Logue, is trying to get the King to speak informally and asks, "Do you know any jokes?" And the King replies by saying "Timing isn't my strong suit."

The meaning is that due to his stammer he does not tell jokes because he would not be able to get to the funny part/the punch line without stuttering. And yet,

Exactly! I couldn't remember what Logue said that the King was responding to. It was a great movie, and a great true-life story. They remained friends for the rest of their lives.

Thank you so much it was really helpful