not true, as agents we receive both Thai Quota and Foreign Quota price list, if the said 20-30% is true its malpractices of business. But the discount issue is true, it happens both Thais and Foreigner, recently sold 30% below than Thai quota to foreigner, its just simple supply and demand. Most Chinese are smart buyers they won't over spend without due diligence
well, on given particular condo foreigner can own 49% units, so its not scarce. And the price difference between Thai and foreign quota is very negligible (just few thousand bath for paper work), unless you choose the hot unit in good positions at presale or someone trying to rip off with resale by gas lighting its value in future. Leasehold are more like status for Thai elites, as the land belongs to the institutions in prime location, but its always extendable with market value payment, so technically no need to worry about it for next 30+30 years