So far as I am able to deduct from the case laws known to me in this regard, a 'trainee' would not be a 'workman' u/s 2(s) of the IDA,1947, if the offer letter states that he would not have any lien on employment after successful completion of his training in the organization and he has been paid stipend only during the period of training.
However, as per the practice described and enumerated under serial no.10 of Part I of the Fifth Schedule to the IDA,1947, keeping such people as trainees continuously for long years so as to deprive them the benefits of permanent employment is certainly an unfair labor practice u/s 25-T.