I did it at the airport before I flew out, it's really quick n simple. Surprisingly (or maybe not), a lot of people flying into BKK did not do it and had to wait in a horrendously long line while it took me just a few minutes to go through immigration.
I honestly don't think it'll happen or they'll figure out some exception. The real estate market is a huge money maker and this would alienate so many potential and actual buyers like the Chinese. It's like tripping over dollars to pick up pennies.
So every foreigner who brought a large amount of money into Thailand to buy property and who has been here at least 180 days for the year has a freakin tax liability?! Oh this is going to get good. 555