Having dived and/or worked with most of the dive shops around Pattaya over recent years I have very little confidence in many of them.
In my mind the best and most proffessional one to do an internship is Real Divers, a small familly run operation. And I believe now they will do it on a pay as you go bassis, avoiding a large initial outlay.
Despite what you may be told by the big shops, there is little or no chance of making a living as a DM in Pattaya. Indeed I have even been asked by one shop to pay a substantial ammount of money to work as a DM on their boat???? (dive south east asia). how stupid do they think people are?
The best you can really hope for in Pattaya is to work for free diving.