Yes. I survive off 700$ a month comfortably, and half of that is excessive spending. But i think it mostly depends how you eat, rent cost which i got lucky on 5k plus less than 1k electric and is nice place..
I have 2 passports. Law is, you must enter/exit the country on that country's passport (so if you are a citizen of Thailand, you are not supposed to enter or exit thailand on your Australian passport, and vice versa --> though i suppose it is possible to do so, i know someone who did but they were worried about the exit thereafter)..
but yes in regards to the ticket could be problematic. I would get the passport renewed, or call the airliner to see what to do.