Salary received by an Indian citizen from Indian Government being his / her employer for rendering services outside India, will be deemed to be accrue or arise from India u/s-9(1)(iii). However, all other perquisites as well as allowances received from Indian Government will be exempted u/s-10(7), irrespective of whether the assessee is a resident or non-resident.
Since TDS has been deducted, though it may not be mandatory u/s-139(1), provided the GTI is below the exemption limits but it will be beneficial to file ITR to claim refund or to carry forward of loss, if any. Besides, a notice may be issued to the assessee for non-filing of ITR since TDS has already been deducted. Moreover, filing of ITR will also be beneficial for getting any loan in future as it's a standard income proof accepted not only in India but globally too.
Hope ur doubt is cleared now...