just got back from a month in los yesterday
spent about 10 days in phuket in 2 different periods.
but spent the rest of the time in the issan.
yes udon and especially nong khai are not all that happening for night life, but it is there, and you will still have a good time. Expats will tell you where the naughty nightlife is.
look around the issan travel by bus do not expect miracles and its very cheap. Hotels girls and food.
it was my 4 trip to the issan and it gets better every time, when you realise this is real thailand and not the one most farangs are exposed to.
i still like patong, but now it is getting to crowded for me
take the plunge and go up the issan you will enjoy the experience.