Thanks Matt. That's right, the franchises are mostly owned by locals. They are trying to set a new world record with regards to 7 Eleven. I believe they are past 6,000 shops already. There are three within 100 meters from where my father lives, and they sell mostly junk food.
As for the roads, the story I've heard is that they had some western advisers during the fifties and sixties. One of the advices they got was to close down local railways and build roads instead, and they did actually make roads where some of the most important canals were. The result is a never ending traffic jam 24/7, which is also the opening hours of the convenience stores. You never run out of traffic and junk food in Bangkok