I very much agree with Diver0001 - because I've seen people get exactly that!
Most companies that offer "MSDT internships" will usually charge money for it, but I know people who've been offered the require MSDT dives and/or training at cost price because they're proving to be valuable members of staff and it is in the company's interest to expand their training capabilities. They pay for required materials and the certification fee, but otherwise the training and/or diving is free of charge. From my experience, the "work in return for training" thing only ever works if an employer sees a good potential return on their investment. Same as DM "work-to-pay" internships.
To the OP - all you can really do is e-mail as many dive centres as you can with a good resumé and their thoughts on your offer. Look at dive locations where particular skills or languages are required (if you have them). I've done this looking for employment in Sharm - e-mailed *everybody*, and occasionally somebody replied.
My point is that to find any kind of "free training", you will have to have something special to offer the dive centre, and even then you might have to a cover a lot of living expenses before your income starts to outweigh your expenditure - apartment to rent, food to buy, pet cat to feed, girlfriend to pay (which is quite normal in some parts of Thailand, actually) - possibly for several months... I know this because I did that - although I never had a Thai girlfriend...!
There are various ways and means of extracting "free training" from the dive industry, but sadly, they are all rather expensive.
Cheers,
C.