This study assessed the subjective well-being (SWB), or welfare, of the elderly in retirement homes in Bangkok, and examined related factors, particularly from the perspective of happiness economics, since the empirical evidence in this aspect is still limited. Primary data was collected by distributing questionnaires and carrying out in-depth interviews between August 2017 and November 2017. In total, 120 participants were included, of which 60 persons were from public retirement homes (44 women and 16 men) and 60 persons from private retirement homes (40 women and 20 men). The cross-sectional data were analyzed using standard descriptive statistics and estimations of logit regressions. The logit regression results reveal that the following were positively related with SWB/welfare in all regressions as hypothesized: a short distance between the retirement home and a temple/hospital, a retirement home located in the participant’s hometown, and interest in obtaining free college courses. Meanwhile, the coefficients on the need for a higher number of care staff were negative. Among the control variables, being female, being older, completing secondary school, and having plenty of money to spend were strongly and positively associated with SWB/welfare. It was noteworthy that receiving a total Barthel ADL index scores of more than 10 and having family and friends visit regularly (once or a few times a week) played an important role in increasing participants’ SWB/welfare in both public and private retirement homes.