how can i work for multiple employers at same time on TN Visa

[krishjavainfo]

Hi,
i am Canadian citizen and currently working on TN visa in usa and it is full time position. i read some where that by getting TN visa for new employer, we can work at same time for both employers.
but second job should be part time and i am bit confused with this. i also found that when i go boarder to get new TN visa i need to inform officer that it is for concurrent employment. does it mean if i dont inform would they cancel first TN visa?

any help is appreciated