The aim of this research was to examine the determinants/factors affecting the well-being of the Thai and Lao people, and the factors that predict the well-being of those respective peoples. Eight hundred and sixty participants were recruited from three major regions of Thailand and Laos and were selected using multistage random sampling. A self-reported well-being questionnaire was developed using the theoretical framework of Maslow's hierarchy of needs, and a questionnaire assessing their perceptions/attitudes concerning the factors affecting their well-being was administered. The major findings were the following: (i) the factors affecting the well-being and the self-reported well-being of Thais and Laotians were significantly different; and (ii) the factors predicting the well-being of Thais included the living and working environment and the availability of medical information and technology at their hospitals. On the other hand, one of the factors predicting the well-being of Laotians was their attitudes toward their society and its cultural values. A comprehensive and system-wide review of mental-health policy planning to improve the well-being of people in Thailand and Laos in accordance with those predicted factors is recommended.