I also prefer receipts, but I now use my girlfriend's membership, so I made the sacrifice of living dangerously and risking being overcharged LOL... for the greater good of accumulating points on her membership.
There are some benefits of using a membership. You can get extra discounts on some items, along with discounts for using some credit cards. For example, a while back, I got a 50 baht discount for using a MasterCard on several occasions. It might balance out for the occasional mistake made at the till. I usually keep an eye on the cash register screen as the items are being scanned. If I hear extra clicks on items, I make an immediate inquiry.