Nice Thai girls work in banks or schools.
You can meet nice girls in the parks on an evening, many of them are out for a jog or a walk. Nongbua Park and Nong Prajak have the aerobics sessions, there are some nice girls there too.
University girls are pleasant as well. Although I never had the chance to frequent the Full Moon bar on the Khon Kaen road in the old days.
Stay away from the countryside lot, they're not bright and their families are only interested in your money. Stick to educated townies.
I have to disagree with a few of your points. For one, if the guy is looking for a genuine Thai/Isaan girl, he is more likely to find her in the country than in the city where he might meet Sino-Thais, half-Chinese/Thai and others who may not be from a pure Thai background.
My former wife was from rural Chiang Mai and was wonderful and was her family. They were not educated, but they were bright. It was more a matter of not having money that held them back from education. Her younger sister, for example, became a nurse. And, her brother's kids both won scholarships at Chulalongkorn. He saved up his money from driving back and forth from the village into Chiang Mai and back. He could not read or write, but he was a very intelligent man of high morals.
My wife, when she came to Canada, studied at a local high school and then a college and became a Personal Nursing Assistant and is making over $80,000 per year today. She had a basic Grade 6 education, and began working for $1/day at a tobacco factory in Sankamphaeng.
Many of the people in surrounding villages have stories much the same as this so I would disagree that they are dimwitted out in the countryside.
However, I will grant you the fact that some of the farangs who come to Thailand looking for a wife are a bit on the dim side, and are shafted by the wily girls who can sniff out a sucker easily.