Among the most prominent features of Thailand's population in recent decades is the rapid growth in the numbers of older persons and their increasing share of the population. Using national survey data, this chapter examines trends in the likely determinants of well-being among elderly Thais, discussing the roles of material well-being; family size; residential dispersion of adult children; living arrangements; age, gender, and education; marital, health, and work status; and formal support. It then discusses the implications of shifts in resources for old-age support in Thailand, including individual, family, community, and government resources.