I have been a non-resident and holding trading account in US. In the year 2018, I sold my stocks and made a profit of $7000. Should I pay tax in US or in my resident country?

Thanks,
SS.

As you said, as a non US resident, in terms of capital gains, you, as a non-resident alien, are not subject to no U.S. capital gains tax. When a non US resident sells investment stocks or securities at a gain, that gain is exempt from U.S. tax unless you are an U.S.resident for tax purposes. The exemption applies equally to long-term assets held for more than 1 year capital gains and short-term capital gains. As an exception to this general tax exemption, gains from the disposition of stock in companies with substantial U.S. real property holdings may be subject to U.S. tax