This paper examines the impact of changes in the structure of the economy, radical changes in economic policy and oil price shocks on the relation between Thailand energy demand and its macroeconomic determinants. The impact of these structural changes on the relationship between energy consumption, income, energy prices and structural variation is examined through unit root and cointegration tests, the cointegration relationship and the error correction model. Methods which endogenize the location of an a prior unknown break point are employed to assess the impact of structural change. In general, the recognition of structural change has lead to some unique insights. In particular, the results of some of the conventional unit root and cointegration tests are reversed once structural changes are recognized. Estimates from the cointegrating regression imply long-run income, price, and structural variation elasticities of 0.568, -0.600 and 1.046 respectively. In comparison, estimates from the error correction model suggest a higher short-run income elasticity (0.788) but lower short-run price and structural variation elasticities (-0.522 and 0.491 respectively). One of the important implications of the estimates pertains to the low price elasticity for aggregate energy demand which implies that the over-pricing of energy as a policy instrument is not likely to be very influential for restraining future energy demand. Additionally, taxes on energy prices are unlikely to achieve government goals for energy conservation and environmental improvement, although they may well be efficient for raising revenue.