My boss very smart. He sensed im asking for more work just for better promotion, he say I can have more work but grade will remain average, he ask do I still want more work.

I say no. He say then you don't deserve a promotion.
I say OK I will do more work with no reward, he say then you haven't been working to your capacity if you have too much time for more work..

Some jobs are just lower paid.
If you want the top salary, you gotta get that skill or fight for it...
Not ask to do more in your capacity and expect a raise.

Toilet cleaner can only earn so much.
You ask to clean more toilet... Can't promote you to be toilet supervisor.
If you want to be toilet supervisor you need the supervision skills..

Sometimes I feel judged by the toilet cleaner. Do you feel that?
So much so that I feel so bad for them.. I try not to go to toilet when they clean...