In theory anywhere outside the mini-map is out of bounds. This can be very close to the fairway in places but sometimes you will go OOB while still on the map.
This happened to me on during am MP game on St. Andrews #14, the par 5. There was a 21 mph wind blowing from about 11 o'clock so the second shot had no chance of clearing the rough. I aimed to the left where I always do in these cases but caught the ding a tad early and was close to the edge of the map, still on it though. However the game decided I was OOB and I took my 4th shot from where the tee shot finished. I played the same shot and stayed well within the map, made a bogie and got a half out of it.
Still annoying to lose a ball that is technically still in play though.