Where are you planning to take the DMT course? If you'll be in Thailand, most of the main destinations (Phuket, Koh Tao) have very comprehensive scuba supply shops that will sell at discount/trade price to DMTs. They prices are usually cheaper there, even without the discount.
The same is true for clothes etc. In Thailand, there was a huge selection of cool diving t-shirts, shorts, jeans, hoodies etc.... all for laughably cheap prices. The funky scuba-themed clothing shops on Koh Tao are some of my favorite shopping in the world...
Don't take spare regs!?! That's a waste of weight and money. Depending on your location, compass, zip ties etc etc are all easily available. You should factor on a
15kg max weight limit when taking regional/national flights around Asian. Leave some space for stuff that you will collect along the way.
If you are going somewhere remote, and aren't sure of your ability to buy stuff once en-situ, then here is a good list for the DMT course and general self-sufficiency as a diver:
a) DSMB. I recommend oral inflate, small capacity (
i.e. Halcyon 3.3ft closed circuit)
b) Finger Reel. 1x30m & 1x 15m reels.
c) LED torch. Decent quality, such as LED Lenser, FAMi or
d) Wet Notes (underwater notepad)
e) Wrist slate.
f) Small - Medium size flat slate (A3 size)
g) Suunto dive compass
h) Storm whistle
i) Digital camera & underwater housing (can rent to customers...but also for your own fun!)
j) Mini laptop/notebook with high capacity (500g) external hard-drive.
k) Several USB memory sticks.
l) Leatherman tool. These are always useful.
..and wetsuit! Depending on where..and when... you are going in Asia, the requirement can be very variable. Also, you will quickly acclimatise and the water will start to feel cold. It isn't the same as a 2 week holiday... you will start to get cold on dives, even in warm 'tropical' waters. In monsoon seasons, with wind and rain, you will be chilled all the time. Also, when diving day-in / day-out, as a DM(T) a wetsuit provides important protection for your skin.
I agree with KathyDee about this. You may have travelled and dived in Asia before... but unless you were diving constantly, for weeks/months, then you won't have appreciated how you will get cold. Trust me on that one
Vietnam & Cambodia - can be cold, (24-26 centigrade)..and a 5mm full suit is needed.
Thailand & Philippines - in monsoon seasons it can get very chilly....a 3mm fully suit is nice.
Malaysia, Borneo & Indonesia - a 3mm suit is nice, but you can get away with shorts and rashguard most of the time.