The primary aim of this research was to study the influence of working environment and employees' motivation on the efficiency of their work performance. This research used a quantitative research approach. The research sample was 400 employees of a textile and clothing industrial factory in Thailand. The study was undertaken between June 1 and August 31, 2018. A questionnaire was used as a data collection tool. The collected data were then analyzed with descriptive statistics including

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... y, percentage, and multiple linear regression. In terms of the sample's profile, most of them were female, between 20-30 years old, single, graduated below the undergraduate level, had working for more than 10 years, received around 15,001-20,000 bath per month. The research findings showed that these employees viewed that the overall working environment was significant for them. When considering at each aspect of the working environment, it was found that the each of the factors including the design of the working environment, structure of the office buildings, work structure, the efficient design of equipment and machines, safety and sanitation of working place, and process, was rated at a high level. As for the employees' motivation, it was found that the overall motivation, and each aspect of motivation including organizational policies and management, working condition, salary, job responsibilities, and progress in work were rated at a high level as well. The results of the hypothesis testing showed that working environment in the aspect of design of the working environment and safety and sanitation of the working place had an influence on the efficiency of the employees' work performance in terms of the quality of the outcome of work.