Tips for getting around:
Forgot to mention, I was in Hatyai, Nakhon Sawan and Prachuap Kiri Khan recently and was surprised to be able to get a GrabCar driver to respond so quickly every time I made a booking. Apparently there are lots of GrabCar (not Grab Taxi) drivers also online in Bkk now. This makes it easier to get from place without having to haggle on the fare with Taxi and TukTuk drivers. Not sure how effective GrabCar (or Uber) will be in Ubon Ratchatani but you can give it a try and let us know how it went