There is nothing wrong in promoting an employee while on leave. In the case of accelerated pay scales, the increment comes automatically and is given to persons on leave also unless otherwise agreed upon at the time of granting leave. In the case of ESI leave, there will not be any condition for granting leave, and therefore, there should not be any confusion regarding granting an increment. However, in other cases, where the increment or promotion is declared following a procedure of appraisal, etc., then the management can hold it until he resumes work.
If, due to the increment, his salary exceeds the limit (15,000 as of now), then he will still be under coverage until the end of the contribution period. That means if you are giving a hike now, he will remain under ESI coverage until 31st March 2014. From April 2014 onwards, he will be out of coverage subject to the salary limit at that time. An employee who becomes out of coverage is eligible to receive medical benefits until the end of the next benefit period. Similarly, an employee who is receiving medical treatment for a particular disease will continue to receive the benefit until the ailment exists.
Regards,
Madhu.T.K