Generic drug manufacturers in Thailand have become particularly active in recent years. There is a clear development trend among local generic producers to catch up with new technology and take advantage of the government’s pro-generic policy at the moment. Several generic manufacturers recently began to develop and market generic versions of various best-seller drugs, despite the fact that some of these drugs are still under valid patents in Thailand. This article introduces some defensive strategies that will allow drug originators to tackle these infringing generics.