Can I ask my employer to pay me early even if it costs him money to employ me?
Why do you want to be paid early?
I don't like my boss, I'm not happy working there
You shouldn't expect to be paid earlier than the payment schedule. Maybe you can sign up for a bank that allows early direct deposit? That way you can get your pay earlier without bothering your boss.
Well there's no need for me to work there, I'm going to tell the boss my contract has ended.
If you don't like your job you should find a new one, but he will pay you when you should get paid. Everyone has a schedule on when the employer pays their employees because that is how things work out.