I always carry a few thousand baht in cash with me, even though I normally pay my bills in supermarkets by scanning QR codes.
However. Twice this week, Makro and Tops, those QR codes would not work, (This payee cannot currently receive payment. Or something like that), and I had to pay in cash.
Also this week I did some haggling for cash and got over 40% reduction in price. I knew they were asking far too much (THB110), as I currently had the same things on order on Lazada for THB40. Cash is still king in my book.
I don't know how true this is, but my GF told me there are always problems paying by QR codes at the end of the month in Makro.