You can, but that just increases the time you are in a queue waiting, as you are not the only one. That can easily add at least a half hour to your wait to get out of the airport.
you have to have a letter from your employer specifically saying you can work remotely. Is a slight headache worth saving about US$1000, and not have any hassles for the next five years?
You apply for the type O visa before you come to Thailand. That gives you the 90 day type O visa you need to open your Thai bank account to transfer in your bt800,000, and after two months apply for your one year extension. It is very easy to do.