the 500K is not negotiable, it's a must have requirement, some consulates only want to see the money in the bank, others want to see it in the bank up to 6 months prior.
each consulate will usually post the processing times for visa applications. So yes if you are in a hurry or have a deadline you should be aware of the processing times.
The process is pretty simple and straightforward, choose your eligible scheme, get paperwork proof, show adequate funds, go to and apply from a country outside Thailand.