In this paper, we propose a smart Advanced Metering Infrastructure (AMI) system for city gas that addresses the limitations of conventional metering methods through wireless communication. Traditional systems, which rely on manual inspection or Power Line Communication (PLC), face constraints such as installation limitations, interference from other electronic devices, privacy concerns, and difficulty in responding to gas leakage incidents. To overcome these challenges, the proposed system employs LTE Cat-M1, a low-power wide-area technology operating on commercial cellular networks, enabling low-power, long-range, and reliable data transmission. A prototype was implemented using an Arm-based SoC board with an integrated multi-sensor smart meter. The multi-sensor module collects flow, temperature, pressure, and image data, which are used to refine and validate metering information. Experimental results confirm that metering data can be reliably transmitted via LTE Cat-M1 and effectively managed by the Meter Data Management System (MDMS), which provides real-time visualization and monitoring. The collected data can be effectively utilized by users to check gas usage and detect anomalies in the metering status.