I see. Yes, you'll definitely need 400,000 baht in the bank and it will need seasoning too. I had to show that the money I transferred to the Kasikorn bank had come from overseas and in order to get the Non O visa based on marriage to a Thai national, it had to sit there for 2 months before my application . I didn't use an agent but some do and I believe they " lend " you the money but then I believe you are then stuck with them for each renewal.
Ah, right. So do you have an Australian passport? Also, have long do you want to stay in Thailand this time and how many trips have you made here before and over what period of time?