I do not believe that that is recommended.
The threaded portion will see the stress point at the bottom of the stem clamp.
I have inquired in the past about using a threaded fork using a quill/threadless adapter and stem to
load the threadless headset instead of the star nut, and was informed that it was a bad idea....
I believe that the quill stem or adapter reinforces the steerer by moving the stress point to the bottom of the quill portion inside the head tube (between the headset bearings.
Plus, I don't believe you would get suitable clamping force on the peaks of the thread pitches with a clamp stem.

I could be incorrect..............