HR Malaysia

First the present company has to served termination notice to the employees.

Then you offer them the new contract which has two type;

1. If the present company going to pay the RB, your new contract is the same with the one you give to new employees.
2. If the prsent company not paying the RB (this normally been decided in the negotiation to take over), then your employment contract must stated that their service is continous and all the benefits can not be less favourable than the present one.

Before that you could also meet up with the employees to have a dialogue session to explain the changes if any.