I have written this before and I will write it again, as it refers to general education and not just English language education:
This has gone on for so long that I am convinced that the Thai powers that be do not actually want the Thai population to learn English. This is because without it they cannot learn about the outside World with its relative free thinking, choice and differing standards, education and values. World News is very limited and filtered through mostly partisan Thai media. Online World news in Thai on You tube etc., seems to be mostly Conspiracy Theory which completely distorts their World View and its politics. Most of the Thai population emerging from the appalling State education system remain backward and blinkered due to having learned little more than Nationalism, and obeyance to monarchy, religion, and military. I think that the Thai Establishment have realised that without English; which is for better or worse the international language, the Thai Masses can be more easily controlled, manipulated, and exploited for cheap labour by their mostly Chinese-Thai masters (who own most of the land and businesses). The 'Elite' can maintain 'hereditary' control as only they can afford decent private and/or overseas education for their children.