This paper presents the design and implementation of a WSN-based system for wave height measurement in the rivers of the Mekong Delta region. The special feature in the proposed system is that the ESP32 microcontroller boards serve as both microcontrollers and wireless transceiver units for data exchange. The ESP-NOW wireless communication protocol, which is a built-in function of the ESP32, is used for data transmission between sensor nodes and central receivers. Our proposed approach achieves two key advantages: (1) simplifying circuit design and reducing costs by eliminating the need for separate wireless transceiver modules; (2) Enabling data transmission at higher speeds than the Zigbee standard by using the ESP-NOW communication protocol. Preliminary tests showed that the proposed system could capture changes in wave amplitudes quite accurately under experimental conditions. The designed sensor nodes are light weight, low cost, and simple in structure, so they could provide a potential solution to address the problem of assessing the impact of waves on riverbank erosion in the Mekong Delta.