To develop a model of healthy aging from the perspective of Thais, a grounded theory approach, including in-depth interviews and focus groups, was used. A purposive sample of 39 community-dwelling adults aged 40–85 years old was interviewed. The Thai healthy aging model composed of three themes: normality, nature, and dharma. In Thai, they are called tham-ma-da, tham-ma-chat, and tham-ma, or “Thai 3Ts”. The theme of normality encompasses subthemes of staying physically active by being involved in plenty of physical activities, and being mentally active with creative and thoughtful hobbies and work. The theme of nature encompasses subthemes of living simply and being careful with money. The theme of dharma encompasses subthemes of enjoyment through helping family and participating in community activities, staying away from stress and worries by talking openly and honestly with someone, making merit, and helping other people without expecting anything in return. A greater understanding of healthy aging is a benefit for older adults and healthcare providers in an intervention-design process. Research can contribute valuable information to shape policy for healthy aging as well.