The senior population quickly grows in many countries, affecting individuals and families. Also, it has a large impact on both the economy and society. The changes have impacted the happiness of the elderly, who should be cared for through health promotion in order for them to be able to care for themselves. This study was aimed to identify the happiness of the elderly, socio-economic status, and health-related factors with the happiness of the elderly in Thailand. This cross-sectional study was performed using the data from the National Statistical Office of Thailand: Report of the survey of elderly in Thailand 2017. Data has been collected from 33,343 individuals by using a structured questionnaire. The multi-level analysis was performed to identify the socio-economic status, health-related factors with the happiness of the elderly in Thailand by controlling the effect of other covariates. The result was presented with an adjusted OR and 96% confidence interval. Among 33,343 individuals of the elderly, 65.93% (95% CI: 0.654-0.664) stated that they were happy. Factor associated with happiness of elderly in Thailand were; income adequate and left for saving (adj.OR=6.50; 95% CI: 5.60 – 7.55, p-value<0.001), the Social-Bound Elderly (adj.OR = 2.08; 95% CI = 1.58-2.73, p-value < 0.001), exercise regularly (adj.OR = 2.08; 95%CI = 1.06-2.20, p-value < 0.001), Self Care of Elderly (adj.OR = 2.32; 95% CI = 2.09-2.59, p-value < 0.001), received health information from an internet (adj.OR = 2.45, 95% CI = 2.07-2.89, p-value < 0.001). A happy senior person can take care of their health, whether by regular exercise, health care, or having a better socio-economic status; therefore, the government should focus on laying down a foundational policy to make the elderly happy. This affects physical and mental health, an important factor in preventing disease and living as an important force in sustainable development.