Can any one help me with the office reopening action plan/SOP post pandemic lockdown?

Can any one help me with the office reopening action plan/SOP post pandemic lockdown?

Since no-one has been through this situation before, I doubt that such a thing would exist.
Every organisation is going to be unique in this respect, so you will need to develop your own action plan for how YOUR organisation is going to handle the return to work.
Use the current requirements of social distancing, increased cleaning, etc in your thinking. Also how you will deal with staff, clients/customers, suppliers, workload, etc. All of these matters can be dealt with in your action plan.

You may take guidance circulars issued by central govt. & respective states and make them as guidance principles and procedures to be adopted strictly in work places. Various circulars thus issued by govts from time to time have been attached in these pages in other links relevant to COVID, you may search & get them.

To resume operations, the following steps have to be followed:
1. Follow the guidelines of the central government (MHA) and the respective State government.
2. Develop guidelines for the staff for attending office.
3. Develop a "Work-From-Home" Policy
4. Design cost-saving and waste-reduction programs.
5. Complete the sanitizing work of the office premises and procure all essentials such as hand wash, sanitizer, face masks, hand gloves etc.,
After asertaining the above, regular operations may be resumed.