A non-resident alien files a form 1040-NR to report and pay US income tax on US-sourced income. US-sourced income is generally income paid to you while you are living and working in the US, regardless of the location of the employer. (In contrast, if you live overseas and work for a US-based employer, that is not US-source income for this purpose.)
You can review the table here for other types of income.
https://www.irs.gov/individuals/international-taxpayers/nonresident-aliens-source-of-income
Your question is not clear and I don't know what you mean exactly by "salary is coming from US job being done remotely?" If you are living in the US and getting paid in the US, it's US income, even if you work at a different location than your employer. Otherwise, you would need to give more details.
