Trigger UI event in Create from the background thread

Is there a correct way to trigger some action on UI thread?
I have a Create’s py extension where I have a timer event that I enqueue using threading.Timer. I detected that timer’s handler is called within a thread other than the main thread (I’ve compared values returned by threading.current_thread().ident ).
My timer’s handler does some UI stuff and Create’s UI get frozen.
When I trigger same action on button click in Create’s extension - all is ok.
Please help.