Westerners increasingly retire outside their home countries, and some venture to developing nations. A growing number go to Thailand, usually after working there or after many tourist visits. The present study examined currently and formerly resident Western retirees in Thailand, with a focus on their reasons for migrating to Thailand, their wellbeing and perceived assimilation, the reasons why some leave, and their long-term welfare needs. The principal data source was an online survey of 152 current and former retirees in Thailand. The major reported motives were low living costs, a warm climate, to escape a disliked home nation, like of the Thai lifestyle and culture, and the availability of attractive sexual partners. Most survey respondents had a Thai spouse or live-in partner. The move apparently works out well for most, at least initially. They report positive wellbeing and feel assimilated, but most live with visa insecurity and their assimilation may be partly illusory, as many reported socialising mainly with other foreigners. The major long-term concerns of Western retired men in Thailand are their health-care and welfare needs, income problems, increasing negative local reactions to the influx of Westerners, and the possibility of visa cancellation that would enforce a move elsewhere.