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
Ironically, according to numerous Thais Ive spoken with, these rules were supposed to target wealthy Thais that took advantage of tax loopholes with overseas investments/income. Go figure.