Nowadays, Wireless Sensor Networks (WSNs) are considered as a most important applications due to its rapid propagation. In an Internet of Things (IoT) network, the messages are exchanged and routed in an open multiple devices, therefore security is one of the major issue. Hence, the most important requirements in IoT networks is integrity of information, optimized energy consumption and data security. All the group members uses the shared symmetric key called Group Key (GK) for maintaining data confidentiality within a group. A forward and backward secrecy are maintained by redistributing the GK while joining and leaving of a group member. But, when consuming the scarce network resources, the key management includes generation and distribution process causes overhead. In this research study, Advanced Encryption Standard (AES) is used to design the lightweight and secure Group Communication (GC) and finally, preserved the data integrity by Public Key Infrastructure (PKI). By using AES-PKI algorithm, the method achieved secure GCs in network against attacks, lower bandwidth utilization and network overhead in key re-distribution and management operations. In addition, the proposed AES-PKI method ensured the data confidentiality by backward and forward secrecy in key distribution method and also effective against the network mobility in scalable IoT networks. The performance of AES-PKI is validated by simulation dynamic results of energy consumption and packet receiving ratio.