http://wefreedive.org/and
ttp://andamanapnea.com/ Are both great. Would 100% recommend them.
I've done AIDA freediving courses through both.
While you're there check out
http://www.phuket-spearfishing.com/All great businesses I've had first hand experience with and its awesome being able to spear and freedive in warm water, no wetsuit and amazing tropical surroundings.
Let me know if you're interested in more info on Phuket, I go there all the time and can put you in touch with people for airport pickup, motorbike rental, accomodation etc. It's not something I get anything out of, I can just help you out.
Have a look in the 'dive trips' section for the Thailand or phuket threads, some good pics there, think there are 2 already and I'm adding a 3rd soon, as I just left Phuket again after staying 2 months.
Email me if you want some more info
camskea@hotmail.comcheers
Cam