Udon Thani province is one of the Thai provinces where being transported or accompanied by a guide is essential. Otherwise, you will be mainly confined to the city which is interesting but you will miss the prettiest perched temple in the area, a nice historic park, waterfalls, a very local floating barge restaurant, lots of things that are tens of kilometers away from the city. Even going to the pink lotus lake, it's not that easy (but doable).