Section 6(1)(i) in The Indian Forest Service (Pay) Rules, 2016
(i)in the case of a Member of Service who is, on the date of such notification or, as the case may be, date of such order, out of India on leave or deputation or foreign service or active service, the said option shall be exercised in writing so as to reach the said authority within three months of the date of his taking charge of his post in India; and