I voted no due to the close proximity to the other patch, and another patch probably won't stick correctly, though it could, you could risk it and see what happens, but the patch on top of another will cause a small bump as your ride, and for that reason you probably should consider tossing it, or use it as a backup spare in your seatbag if you know that the new patch has stuck extremely well over the old patch.

However, usually I patch my tubes, there's no sense in throwing away a tube just because of a hole or two or three, the only reason people do that is because they are not confident in their patching abilities. I once had a tube with over a dozen patches on it, as long as the tube is pliable, doesn't stick to the inside of the tire, the valve stem works, the tube is good for repair.

I've never had a patch fail, like that one tube that had about 15 patches on it I used that tube for about 7 years, and it never leaked from any of the patches...unless it got another hole of course! Butyl tubes last at least 7 years to as long as 15 years assuming no fatal damage, so if you can keep patching a tube, they're safe to do so for at least 7 years.

One person mentioned a car patch, not the same thing. A car has to be able to run at the speed rating of the tire, most tires are around 112 to 118 mph, thus with two patches over another it would fail the speed rating, and that's why it's illegal to put a patch on top of another patch on any car tire. The last I checked, bicycles do not do 112 to 118 mph unless you're skydiving with it, but even then, since the tire isn't rotating at that speed on the road it isn't generating any heat, thus the tire would be fine when you landed.