They want you to work, but if you can work your non entitled to collect disability, pretty simple.
They have a Work Incentive program where basically you still get 50% ssi match of your supplemental income over $64 a month.
If you earn an extra $240 you should lose $100 in benefits.
Here's their (rather old) information page
http://www.ssa.gov/disabilityresearch/wi...
The guidelines are fairly straight forward and it's something that you should have considered before accepting the job. It seems as though your choices are going for more hours at work to increase your income, and forget about SSI, or keep the free money and find someone who will pay you under the table to work for them.
Well the choice is yours here.
Make a decision and stop worrying over this matter.
Best of luck
It is designed for people who are disabled and can't work.