Good questions and since I live here in Bangkok I will try to provide some answers:
Websites can be decieving-
The situation here has gone downhill a little.
http//www.blacklotus-bangkok.com/
http://www.barbar-bangkok.com/
http://www.demoniabangkok.com/domina_thailand.html -------------
If you enjoy paying high prices for drinks, a ripoff entry fee, and having sessions with supposed Mistresses that really do not know what they are doing - then go to these places. Blacklotus is just the dungeon inside barbar. The girls make better slavegirls than Mistresses. Demonia is a little more customer friendly than Bar Bar. And my vote for the worst ripoff - poor attitude SM establishment in Thailand is The Castle in Pattaya. Great facility but the girls and staff that work there are greedy money bitches that do not care about customer satisfaction - only about how much money they can get from you.
http://www.thaimistress.net/
Mistress Midori is a good person and her dungeon is probably one of the best in Asia. But her website is rarely updated, there have been many problems of being able to contact her by email, and her stable and quantity of Mistresses is always changing. Her best looking Mistress(Pai Ling) is on leave. But if you can reach her - I would recommend.
http://www.thaidomina.com/
I have sessioned with Nurie and Femina before and can vouch that they are probably some of the best Mistresses you are going to get in Thailand. Still not even close to Japan though. Have not seen the dungeon but have not heard anything bad about them in Thailand.
http://www.asiadomina.com/mistressjune.html
Changed name to Thaigoddessx. - Their hottest Mistress Natasha is gone and what is left I cannot comment on. Maybe others here can comment.
http://www.thaimistressmaya.com/
Bad reviews here. Cheap price = bad service = should stay away.
Good Luck