500.000 is probably based on a monthly income around 40.000 during one year, so anything lower than that (from my own point of view) should raise concerns from the commissioner. As said before, 30.000 baht will most likely not cover the living costs including internet, rent, travel, food and most important, health insurance.
I just got approved, applying from Hanoi but I was also required to send additional documents, showcasing bank statement for the last 3 months even thou I already sent a statement showing the require amount with liquid funds present in the account..