In this paper we propose a new noncoherent relay selection strategy for two-way relay cooperative networks. In our proposed scenario, channel state information (CSI) or feedback link is not needed, neither for relay selection nor for data detection. We assume Mary frequency shift keying (FSK) modulation for our transmission scheme and decode-and-forward (DF) protocol for our system relaying method. Relay selection is performed based on a min-max criterion on the received instantaneous signal energies at the relay nodes. Furthermore, by using energy detectors at both destination nodes the transmitted signal is decoded. We present a closed-form formula for the average symbol error rate (ASER) of the proposed noncoherent selection method. We also provide high signal-to-noise-ratio (SNR) analysis and the achievable diversity order for the proposed selection method. Finally we present a simulation study to corroborate the analytical results and to demonstrate the performance of the introduced noncoherent selection method.