As an EMT and CPR/First Aid/AED (Automated External Defibrillator) and BLS instructor, when I first came to Thailand it troubled me to hear the rumor that one must be a Thai doctor to legally use an AED in Thailand. It is something I found very odd since the whole point of an AED was that it was to be used by laypersons in the field prior to the arrival of individuals with more advanced training. So over the years I have been watching this issue closely. I have yet to see anyone show any document suggesting AED's were illegal if used as intended, by laypersons.

There has been some discussions on Thaivisa forums about this previously, none of which provided any substantive evidence but relied purely on conjecture :

http://www.thaivisa.com/forum/topic/288671-aed-automated-external-defibrillator/

http://www.thaivisa.com/forum/topic/657469-elderly-american-dies-from-a-heart-attack-at-a-barber-salon/

http://www.thaivisa.com/forum/topic/241146-illegal-to-use-heart-defibrillator-in-thailand/

Now recently I have come across some interesting news items which suggests pretty strongly that the "Thai doctor only" rule was in fact a myth, probably created due to the common believe that Thailand lacks thorough "good Samaritan" laws.

Here is an article where they were recently installed in a shopping mall: http://www.thephuketnews.com/central-festival-phuket-gets-life-saving-defibrillators-42660.php

Here are some photos from the Thai Resuscitation Council website where medical staff are teaching lifeguards and other lay rescuer to use AED's:

Here is an AED instruction video in Thai by Bangkok Hospital:

I would say that puts the myth to bed. I would like to hear if anyone else has experience with this.

Until recently they were not found or used in Thailand, glad to hear they have started installing them.

AFAIK there has never been a "law" surrounding them one way or the other. Obviously need to be used by persons who know how/have been trained but as you note that does not require prior medical training, just training in BLS.