Hi Skim - Respect for your decision.
The Philis (i was in the Visayas, the area in the middle) are cheap, have good diving, quite a Western dive community which should allow you more easy to find a job at the end of the day and various place you can try to learn the skills / monetize them if acquired (do a search for Moalboal, Alona Beach, Apo Island, Malapascua).
Manado on Sulawesi, Indonesia has probably even better diving, its Bunaken park is one of the must dives in the world. Other sites (Bankga, Ganggha Isl) are opening up now as well, providing even more great diving (and perhaps, demand for qualified instructors). It is a micro dive industry.
Thailand's best diving is off-shore and reached by liveaboards (unless you want to consider Ko Tao - I would not) so that may be a bit harder with a view on getting your training in. The Phi Phis had nice diving but I guess that place will take some time to re-emerge.
There is tons of info on this site - sure you'll find what you need.
All the best, happy diving! Arie.