Dear Mohan,
The implications will vary depending on your status in those establishments. Are you treated as employee ? Most probably not. Remuneration or fees are not 'salary & wages' . At best you can be considered as 'consultant' or some such portfolio. It could be a 'part time employee', underline "employee' which matters in this context. Secondly, what is the status of those estts., what is applicable for them- Factory, shops, institutions, NGO. Are they regd. under ESIC & EPF Acts ? Better ask them, they'll know the answer to your query, rather they'll decide what is applicable to you. Ascertaiin the relevant info. from the cos. and revert