Yes Bob, you have asked the right person having sampled over 100 there over the years.
If you like the quiet, polite, beautiful pale skin types you can not go past Nongkai as Big Nok recomended.
Probably my favorites from Issan though you do get better in the northern region, specifically CM, CR and Lampang if white and polite is your thing.
In Mukdahan and Sakon Nakon you will find that dog is on the menu. I dont know if it is related but those girls from there have the smoothest silkiest skin in all of Thailand. Often interbred a few generations back with the Vietnamese which also might explain both the taste for dog and the silky skin. Black dog is favored for its taste.
Central Issan have many friendly beautiful girls, more of a Latte type skin tone, a little bow legged from working on the rice fields which also gives them pert behinds with almost a rubbery texture.
Southern Isaan have the least attractive girls in my opinion, Burirum, Sisaket and Surin, very dark and with more Khmer mixed in so their facial features are not as good. But what they lack in looks they more than make up for in sexual appetite for Farangs. You will find a higher proportion of these girls in Pattaya Bars than from anywhere else. Dont be surprised if you are walking down the street and one pops out of nowhere and applies the squirrel grip to you.
Ubon borders Cambodia but also Laos so you get more of a mixed bag of looks in Ubon. Many stunners there happy to meet someone like Bob.
Korat also gives you a bit of a mix as they have a large population of Central Thais that have crossbred with the Issan people. Some stunners.
Good luck Bob, not that you will need it in Issan. Take a stick, you will need it to fight them off.