One or the other. Easier to have 800,000 BHT in your Thai bank account. 2 months before and 3 months after. Minimum balance 400,000 BHT. More work the other way but possible
Go to Immigration office yourself. This way you know for sure it is done. Otherwise go to a Visa company but I am sure you will pay more. You do not want a fine or face possible deportation.
What I wrote was if you did not have an income. I was mistaken with the months prior to and after. It is 2 months before and 3 months after. Go to immigration now and ask them.