My take ....
From Bangkok Post article. About 6 weeks ago the government said they would be cracking down on mule accounts. The accounts were related to foreign entities running fake Thai businesses and property transactions. They bankroll a Thai person to, for example, start a motorbike rental agency. They make all the money, pay little or no tax because they rent to foreigners. No way to trace actual income. The Thai makes a little, they're happy, the foreigner makes a bundle. The meat of the article was aimed at businesses in Bangkok. Restaurants, property rentals, realty agents, etc. I think the immigration agencies are just being cautious for now. What they are doing isn't taking much away from the tax base because you make a bit of interest money having 800K in the bank. Furthermore, foreigners with embassies that give an income verification letter need not have 800K deposited. Being an American, my embassy is too lazy to help us.