Small repairs, I just use plain waxed dental floss and a regular hand needle. Carefully go back through the same holes that were originally stitched. Have a pair of pliers handy to help pull the needle though any thick layers of cloth. If you're going to use a sewing machine, then you need to use an actual sail thread like V69 polyester or nylon thread. But for hand stitching, dental floss is super strong and works great. I've used it many times and it's comes in a case with a built in cutting tool, so I always just keep a roll of it with a needle in my tool box.