This thesis consists of four independent chapters each of which addresses the relationship between clientelism and social policy in relation to welfare state development from different perspectives. The overarching research question examines whether the adoption of such policies leads to de-clientelisation, and, if so, to what extent. The research extensively draws upon both cross-national data and that from Thailand between 2000-2012 during which populist welfare policies have gained significant influence on political development. Chapter 1 employs a global dataset of developing countries to offer a comparative perspective on the subject and shows that political parties generally trade-off between social policy and their engagement in clientelism. The latter three chapters take Thailand as a case study empirically investigate clientelist mechanisms at different geographic levels. Focusing on the household level, Chapter 2 evaluates the role of patron-client relations in determining access to the Thailand Village Fund based on the Socio-Economic Household Surveys. The provincial level is examined in Chapter 3 which studies economic and political determinants of two types of provincial-level distributive transfers: social policy spending and discretionary spending. Chapter 4 examines the clientelist mechanism at the national level through an assessment of the electoral linkage dynamics by measuring changes in personal votes. The findings show some degree of resilience of clientelist relations as they intervene with social policy allocation, particularly at local level. The global trend contrasts with the case of Thailand where, as in-depth analyses of the latter three chapters have shown, clientelist relations often persist and convert into a new form, for example the southern model of welfare regimes.