> Most Thais can get by with $500 USD.

As local, I can confirm this. Though it was roughly three years ago, ~$400 a month back then could get me a very comfortable life in outer area of Bangkok (Onnut), this includes an apartment with to-the-door food service, air conditioning, parking slot, 10 minutes walk to the BTS (train station) and 16Mbps internet. No pool, though!

The trick is to rent an apartment within BTS range at x minutes of walking in an outer area of Bangkok, where x is >= 10. An apartment with 5 minutes walk to the BTS can cost about $200 to $400, but past certain point in the same Soi, the cost could be reduced by more than 50%.

The cost could get much cheaper if you cook. Food are ridiculous cheap, but food ingredients are even more cheaper.