What should I consider when applying for the DTV visa through the Thai Embassy in Australia regarding flight information and bank balance requirements?

Hi DVT Group, a few questions i need help with. When applying for the DTV via the Thai Embassy website in Aust, it requests flight dates including a return date. If buying a one way ticket what should this date be? Also, can you provide a flight number that has not yet been booked or do you recommend paying for flights before the DTV has been approved? Finally, is it a requirement to a minimum balance of 500,000 THB (approximately 22,985 AUD) in your bank account for at least three months prior to application?