Little did I know I would have two posts on salt on this blog but there appears to be some interest in it.
First, many have asked about the salty soil used in the salt extraction process below. I.E.- can you use this technique on all soil or is there something special about this soil in particular? The answer is that there is something special about this soil in particular. This region of Thailand sits on a salt dome so there is quite a bit of salty soil, but this is certainly not true for all of Thailand. It all has to do with geology/geomorphology, but that is about the extent of my knowledge. Wikipedia has a neat little article on salt and briefly mentions some other ways salt is extracted around the world. Also, this book on salt suddenly seems a lot more interesting now.
Lastly I wanted to mention an article recently in the Mekong Times on salt production in Cambodia and export to Vietnam.