I've lived in Thailand for almost twenty years, I've been to every corner of the country. Sure, there's some nice places in Isaan, especially along the Mekong, and Loei in particular is very pretty. However, in the main it is flat barren land given over mainly to rice farming. Education standards are low and poverty is high. My point was that if a westerner is going to sink money into land/property in Thailand I feel it's better to do it in a more pleasant environment.
If you're going to invest in a house, do it in a good area. Up north Phetchabun way, or out west Kanchanaburi or Ratchaburi. Not in that endless rice field called Isaan
If you've done any form of extension in Thailand before you would know you have to state the reason for the extension on the TM7 form, so whether they know or not, you have to tell them, and then sign the form. Do you have something to hide?
No you can only extend 12 months. But what's the point of wanting a lesser extension if you're leaving? The cost would be the same. All extensions are 1900 baht