Income tax

He is non-resident as he is not in India during the previous year 14-15 for >=182 days

Since he (being a citizen of India) left india for employment purpose, therefore that limit of 182 days wont apply & he would be treated as non resident from the date he left india.

Agreed with Miss Poornima Madhava  & he will be required to file ITR if his GTI exceeds the maximum exemption limit applicable in his / her case for the A.Y. 2015-16..

for being employed outside india... where the period of stay is undefined.. uncertain

@ Mohit : Resident..

As per Sec-6(1),aAn individual will be a "Resident" if he satisfies any one or both of the conditions mentioned below :

(a) who's period of stay in India during P.Y is 182 days or more, or / &

(b) who's period of stay in India is 60 days or more during P.Y. & 365 days or more during 4 years immediately preceding the P.Y.

As far as condition (b) is concerned, it is applicable only in case of foreign citizens, indian citizens leaving India for reasons other than employment or as a member of the crew of an Indian Ship & Indian citizens or persons of Indian origin coming to India for reasons other than visit purpose.

@ CMA Vivek Jaiswal : Employment purpose means for the purpose of employment & not for taking employment. In other words, the individual may be an employed or unemployed person in India. 

Hope ur doubt is cleared now.