I think only one fold would be better. Serging is a very good idea for the edge. But the corners will be very bulky. Here is how I handled the corners on one very large one I made. I folded the corner of the cloth RST on the diagonal. Put it under the machine with the folded edge going into the needle first. The tip of that triangle needs to be at a predetermined distance from the needle. Best to mark this spot so all corners turn out equally. Sew across corner. Your sewing line will be at right angles to the fold. Then check it to see that it will lay flat. Trim seam and press open as best you can. Trim as much as you dare at the tip without cutting the sewing thread, and open that seam. Turn corner right side out. Now you have a flat corner with as little bulk as possible.
The one I made was 8 feet long. Two years ago we were there for Thanksgiving-Hanukkah party and the candles stayed burning while we played the gift game. A napkin caught fire and a hole was burnt into the table cloth. The next morning the maid threw the cloth into the trash. I felt sooo bad because I could have shortened the cloth for another table.