DEAR DEEPAK K S,

In neet bulletin or prospectus it not clearly mentioned that what type of correction is allowed at the time of correction of application form .so no one can confirm that you can allowed to change your thumb impression or not at the time of correction period .may be they allow or not.

but if at the correction period they not allowed you to change your thumb impression then you can talk with the customer care regarding this ,may be they help you regarding your problem.