In theory it may be possible to legitimately do paid consulting work for a third-party company under the business license of the company that has issued your res permit. But this requires the cooperation of your employer, and also that they have consulting for the proper industry in the scope of their business license. And the payment structure is different. You wouldn't be able to be paid directly by the third-party company; it would have to be recorded as revenue to the company that issued your business license. And there will be taxes not just on your income, but likely profit taxes to the company that recorded it as revenue.