In 2011, Thailand experienced its worst flooding in decades; it caused widespread damages, and a considerable loss of life. Using data from the Thai Household Socio-Economic Survey (THSES), this paper analyses its economic impacts. In the 2012 THSES, households answered a set of questions on the extent of flooding they experienced in the 12 months prior. As the same households are followed over time, the timing of the survey and its panel structure allows us to analyse household welfare before and after the flood, for both affected households and for those who were not directly flooded. We can thus measure the true impact of the disaster on income, expenditure, assets, debt and savings levels as well as labour market outcomes. We analyse flood impacts across different socio-economic groups and livelihoods, and identify spillover effects on those households that were not directly affected by the flooding.