Tds on iinterest in nro saving account

I request comments and advise on the following:

My son is NRI living abroad.He has a Nro account where in income generated in India is credited.

Is TDS is applicable on interest even if amount of interest is not likely to increase Rs 10000 in a year.

He is filing Income tax return in India but income is not exceeding taxable limit

Even on interest of Rs 84.38 TDS of Rs 26.08 has been deducted.

My question is whether deduction is valid

If it is valid can it be avoided by submitting Form 15G PAN has been submitted

Please help and advise ruling

Thanks