I don't blame those who do it. They found an empty table and are making sure it will still be free after they've bought their food. When with my wife, we will look for a free table before buying the coupons / cash card, and then one of us will sit at it while the other buys them and gets the food. I see no difference between leaving a person at the table, or placing an object on it to "reserve" it. I usually avoid food courts when I'm on my own, however, as I never have anything I can leave on a table that I don't want stolen, or doesn't look like rubbish that will be thrown away or ignored. For that reason, I've always thought that when you buy your coupon / cash card you should get some sort of place marker that you can leave on the table indicating that it's taken. The same goes for fast food restaurants when they're busy. Grab a place marker by the door and put in on a table before ordering your food. If I had a baht for every time there's been plenty of empty tables when I go in, but by the time I've been served, they're all taken, so I'm left walking around with a tray of food asking people if I can sit at their table, I'd have sagging pockets.