There are few options
1- You must have 800 000 in the bank for at least 2 months which in your case it may be difficult if you don't have longer visa. But you may open an account and put the fund in it and wait. You may have to exit the country one time and re enter again and get another 30 days visa. At this time you had the money in the bank for more than 2 months.
2- If you are on pension and your pay is more than 65000 Bhat a month. You can get a letter from your Embassy and can immediately apply for Non O if hopefully they will still do it. That is how I am going to try.
3- I heard there are agents that charge you more money and they will manage everything.
Good luck