Originally Posted by
Smiles
Actually the most often used is "Isaan", so that's four variations.
They are all correct really because all you are doing when you use english letters for 'Isaan' (et al) to pronounce it you're simply using phonetics.
The Thai spelling for 'E-san' (et al) is "อีสาน", but using english phonetic sounds for all your examples are pretty much OK to speak or write.
I think "Isaan" is probably the best phonetic attempt to getting the sound of the word right: When Thais say "isaan" there is quite a long and hard sound (almost like an extended "isarrrrn") with the two 'a's helping to get the rather harsh sounding more correct.