If your association is already a registered body and the registration is in current, then there is no necessity for re-registration especially for inclusion of new members.
The new members can be admitted by entering their particulars in the register kept in the society.
If some amendments are to be carried out in the bye laws, then a resolution to that effect has to be moved in the general meeting and the copy of the resolution along with the copy minutes (if necessary) should be enclosed with an application to the registrar of cooperative societies for their approval for incorporating the necessary amendments in the bey laws of your society.
For all such things a resolution in the meeting of the society is essential, in the resolution the necessary changes or modifications can be approved by the members attending the meeting but with coram.