Isaan borders Laos and Cambodia and has its own culture and dialect. It is one of the poorest parts of Thailand, but also the happiest for the people. Traditional folk dances originate from Isaan, as well as some amazing food. There are 4 major cities in Isaan, each with its own unique aspects and differences, so any visit will be a great experience if you travel across Southeast Asia. Here's a summary of Isaac's "Big Four."
Udon Thani is the furthest north and is the gateway to Laos. Often travelers from the south stay overnight in Udon Thani before traveling to Laos. It is probably Udon Thani who is probably concerned with Isaan's development. It has small shops, big hotels and an entertainment sector that is much more tourist oriented than the other cities of Isaac. Udon Thani is a relatively foreign population, made up of Expats settled in Thailand. Walking is easy, so take some time to this wonderful town.
It is smaller than Udon Thani in most respects, but with that, it makes sense that Udon Thani cannot repeat it. Khon Kaen University is famous because many students from all over Thailand come to study Khon Kaen. Like Udon Thani, it has retail, big hotels and a good nightlife. Khon Kaen is distinguished by the fact that most of the nightlife is aimed at Thailand especially with the large population of the University. Some bars and clubs are becoming more popular in the spring as the city expands and the new Expat population is welcomed.
Nakhon Ratchasima is characterized by being a bridge between Laos culture and Thai culture. The true cross of culture. It is located west of Isaan and is known as Korat especially among foreigners. Nakhon Ratchasima is a fast-growing retail hub, so close to Cambodia it makes a great import and export location. It is a huge city, compared to 4 universities and many cities in the province of Korat, Thailand.
Ubon Ratchathani is located in the southeast corner of Isaac and is very close to the borders of Laos and Cambodia. It is the most religious province in the province and a well-known Buddhist area. This is the famous candle festival held every year in July, which is the perfect time to visit. There are many temples in the area to experience the culture of Isaan. What you won't find here is the developed areas of Khon Kaen and Udon Thani.
The Isaan region is worth a visit if you travel through Thailand and want a quieter experience than the hustle and bustle of tourist areas. I would recommend visiting any of the above cities.