That's a question for your immigration office. Some will require it to be in a single transfer, and some will allow multiple transfers to meet the requirement. You need to ask your immigration office.
SunnyPhoenix2325 You apply when the money has been in your bank account long enough. You apply at an immigration office. It's called an extension, not a new visa from an embassy outside of Thailand.
There's no embassy to visit inside of Thailand, that wouldn't make sense.
You can get one extension each entry, in theory. But immigration doesn't want anything to do with the DTV so they purposely make it so difficult you won't want to do it. Just leave and return every 180 days.