Orthogonal frequency division multiplexingindex modulation (OFDM-IM) is an upcoming technology for B5G/6G wireless networks. It is considered a competitive candidate due to its advantages in communication efficiency and signal transmission spectral efficiency. However, as a novel multicarrier modulation technique, OFDM-IM still inherits the problem of high power amplifier (HPA) cost caused by the distortion from its enormous Peak-to-Average Power Ratio (PAPR) when passing through non-linear devices. In this study, we propose a novel scheme called Walsh-Hadamard Transformed OFDM-IM (WHT-OFDM-IM) to improve system performance and combat the issue of PAPR in multiple subcarrier and multiple activated subcarrier scenarios. The simulation results demonstrate that WHT can significantly enhance communication efficiency and effectively decrease HPA costs. WHT-OFDM-IM demonstrates superior performance in PAPR and BER compared to conventional OFDMIM, and has great potential for future wireless networks.