Feline leukaemia virus (FeLV) is a retrovirus associated with fatal disease in cats with infection in its progressive form. Although there are numerous reports on the occurrence of FeLV in the feline population worldwide, there is a paucity of data in Asia. In this study, we assessed the circulation of FeLV by ELISA and nested PCR in cats from different countries in Southeast Asia (i.e., Thailand, Malaysia, Singapore, Philippines, Indonesia and Vietnam) and Taiwan during 2017-2018. Forty-seven cats were positive to FeLV by antigen or provirus detection, but 32 samples were considered truly positive on the basis of positive molecular testing. Frequency of occurrence of FeLV proviral DNA ranged from 0% (0/43 positive samples) in Indonesia to 18.5% (22/119 positive samples) in Thailand. A statistically significant association (p < 0.05) was found between country of cats origin, age, lifestyle, abnormal oral mucosa, and FeLV molecular positive results. In-depth studies are needed in other countries in Southeast Asia to elucidate the mosaic of knowledge about FeLV epidemiology.