You probably would have been better of if applying in your homecountry where the bulk of the documentation is originating from, then the visa Officer, would be accustomed with the way the documents look, and have easier options to validate the documents
The 500.000 Baht has to be in a readily available account, when you have access to the money immediately, for example if you get rushed to hospital and have to pay upfront, before treatment.
No all savings accounts allows that.
It is the amount (500.000 Baht) that is important, not if there are regular payments to the account
Read the website of the desired Thai Embassy, and search the group for that specific Embassy, there are loads of posts allready, that adresses that issue.
Don’t leave Thailand until you have used the 30 day extension option, easy done at the nearest Immigration office for 1900 baht, which also is cheaper than leaving Thailand with the risk being denied entry.
You are a grown up person, so take control over your life and do it yourself, no need to use a agent and support corruption.
There are many many posts in the group, which tell how it is done, just use the search bar.
If you are respectful, polite and dress properly, most Immigration Officers will be help you if you should have missed something, and some Immigration Offices have helpful volunteer’s and some even have a hand-out, telling everything.
And you will be proud of yourself, when you made it yourself.
Very bad idea, has been reported that it lead to rejection, even in 2 attempts.
Take control of your live, save the expense of a agent fee, and do the application yourself as you are meant to.
Remember you need to be outside of Thailand, and in the country you apply in, during the whole visa processing, from the day you apply, until the day you get the visa / rejected.