The forfeited shares were originally issued at a premium of 20\%, making the issue price per share:
\[
Rs.10 + Rs.2 = Rs.12.
\]
The shareholder did not pay the first call of Rs.3 and the final call of Rs.1, leaving an unpaid amount:
\[
Rs.3 + Rs.1 = Rs.4.
\]
The amount already paid by the shareholder includes the application and allotment money, including the premium:
\[
Rs.12 - Rs.4 = Rs.8.
\]
For the shares to be reissued, the minimum price must cover the unpaid amount of Rs.4:
\[
{Minimum Reissue Price} = Rs.4.
\]
Conclusion:
The minimum price per share at which the shares can be reissued is \( Rs.4 \).