this visa only became available July 15th so all the details are still being researched concerning future requirements and restrictions. The first time for the 180 day extension hasn't even happened yet. It is that brand new.
it is a five year visa. There are already people trying to scam the requirements. Regulations will be put in place to address those loopholes. Grandfathered in means you come under the rules and regulations in place when you first received it, not regulations added in the future.
You can not extend your entry stamp in Bangkok until you have 45 days, or less left on your entry stamp. Other locations in the country require less than 30 days, and a few locations require that you have less than 7 days left. You can not immediately extend your entry.