Since the employee has not tendered his resignation, he is still in employment until his service is terminated.
His service can be terminated due to habitual absenteeism but by a procedure of law. First, the employer needs to ask the employee to join duties (few times). If the employee does not respond, then issue charge sheet, initiate domestic enquiry and then terminate.
From the situation, it seems that the employee is still in service (though absent) as he has not yet tendered resignation.
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