I moved to Thailand full time in 1999. At that time, I think the percentage of mom-and-pop shops was much greater. It was my experience that many of the shops sold out-of-date products, turned the air conditioning and refrigeration off at night, were open irregular days/hours and were quite often dirty. All that seemed to change with the proliferation of 7-11. Given a choice, people started choosing 7-11 over the mom-and-pop shops, not because of price, but because of the quality, variety and consistency of the products, as well as the cleanliness of the staff and facilities.
It was the same with all the pumps and Jet. Once people were given a choice between PTT, Shell, Caltex and all the other crappy old pumps and a nice Jet pump with big, clean bathrooms, good parking, Amazon coffee shops and great "Jiffy" stores, people voted with their feet. Most all the pumps started improving and finally PTT bought/merged/whatever with Jet.
The consumer benefited greatly in both cases. Everyone had to step up their game.
You claim there are 11,983 7-11s in Thailand as if that's something bad. Would it be better if there were fewer? In any event, over half are owned by franchisees.
I don't hear much about people getting sick from the food at 7-11, and I doubt very much the people think they are buying heath food. It's iensinexpve, filling and tasty which is what people buying it want. I went through one of the plants that made some of the heat & eat stuff about ten years ago and it was pretty impressive by any standard.