Have a look at Koh Tao. Busy dive destination so good prices, lots of hands on experience and good post graduation employment opportunities.
Some good options available on:
http://www.simplelifedivers.com/scubainternshipsthailand/ over 7 years ago
New Heaven Dive School has a good Dive Master internship
http://www.newheavendiveschool.com/ and the recommend a minimum of 6 weeks:
We recommend a minimum of 6 weeks to complete this course although less time is needed if you have a lot of diving experience. During this time you will learn how to be supervising general diving activities for certified divers eventually leading certified divers on fun dives. As well as this you will assist different instructors with student divers in training. The third component of this course is to improve your skills and test your limits in the water. You will be required to perform a variety of swim tests to check your endurance and physical fitness. You will also learn how to demonstrate dive skills at an instructor level, which will also prepare you to move up to the next level in the dive profession, instructor. over 7 years ago
Both quite good places but i'd recommend a smaller outfit like DJL: http://www.djldiving.com/Divemaster_Internship.html
Mainly because they're smaller than the rest so they pay you more attention and this makes it easier. Also they normally have quiet a few interns so you have a nice atmosphere. If Moneys no object Coral grand is good but that is normally for elder married couples. If your young i'd say DJL because you're right in the heart of Koh Tao's sariee scene as well. over 7 years agoAnswered by Johnny via Travellr.com