Because they've been conditioned to 'know' they are only manual labourers. It's a class system - not unlike the UK's. Sure some Sombat from Issan might be able to work hard, use his wits and do better than his brothers and sisters - and many do. But the reality is that the earning band here - even working for yourself - is going to be 6,000 - 15,000 per month, with most falling into the lower end. So even an undergrad from a 'middle class' Thai-Chinese family can't earn much more than that. Kind of zaps any initiative in'it? Wealth in Thailand is gained through only one avenue - a semi-feudal and corrupt patronage system. The chinkier and more connected you are the better. And everyone in that extended family system knows which side their bread is buttered.
My mind is not for rent to any God or Government, There's no hope for your discontent - the changes are permanent!