<p>Urbanization and living lifestyles have increased water demand and consumption, and water-saving practice is one solution to secure freshwater resources. While psychological drivers play a significant role in shaping individuals’ water use decisions, there are key factors that influence water conservation behavior (WCB). However, knowledge of these remains limited, and understanding them deeper can help identify important barriers to action and design more effective interventions and policies that encourage people to use water sustainably. This study aims to understand WCBs and explore the factors influencing condominium residents’ behavior in Bangkok, Thailand, using an extended version of the theory of planned behavior (TPB) and theory of reasoned action (TRA), adding “information effects” (IEs) which have received less attention in previous studies to the original model for water curtailment and water efficiency, respectively. Data from 210 respondents living in condominiums in five highly populated districts of Bangkok were collected using structured questionnaires and analyzed using structural equation modeling. The results revealed that water curtailment was significantly affected by sociodemographic factors, namely education, age, income, and occupation. Moreover, perceived behavioral control was also a significantly outstanding influence on water curtailment, with 59% of the variance in behavioral intention. On the other hand, attitude and IE were powerful influences on water efficiency, with 46% of the variance in behavioral intention. This information is beneficial to policymakers in prioritizing initiatives that raise environmental awareness and educate the public on the advantages of water conservation and in promoting the installation of water-saving devices, which would not only reduce water consumption but also foster long-term sustainable water use behaviors across communities.</p>