시간이 겹치지 않아도 불법입니다.
If you claim to work at two different jobs at the same time, it’s considered fraud. Even if you say you’re working different hours for each job, people will likely doubt that claim. Companies usually require you to disclose if you have another job, so not disclosing it would be fraud. Even if it’s not explicitly stated, it’s generally understood that you won’t have other jobs and will give your full attention to your current job. There can also be conflict of interest issues if your two employers are connected in any way.
In the US, employers ask you to fill out a W-4 form, which asks about multiple jobs. Lying on the W-4 is illegal and can result in a large tax liability because your employers won’t withhold enough taxes.