I'm 5'6" 170lbs and medium AK jackets fit nice and loose.
I have last years AK Stagger, and I originally ordered the Medium (5'6", 155lbs) and it was HUGE. Changed it out for a small and it fits pretty well, comfortably loose.
You being 5'10" - you might want the medium, but it depends on how loose/long you like to wear your jackets.
Go to a shop and try it on.