Modern plant breeding is classified into three types of breeding; conventional, mutation and transgenic. In one way, mutation breeding serves as a global focal point for nuclear cooperation, mobilizing peaceful applications of nuclear science and technology for critical needs in developing countries, including Thailand. The main objective of mutation breeding in Thailand is to identify high yielding food crop germplasm that can contribute to sustainable food security with a major focus on cereals (rice, grain legume), vegetables (water melon, chili) and ornamental (orchid, chrysanthemum). Plant mutation breeding requires genetic variation which is a source of evolution. Mutation induction creates a new variant that is different from the parent and the induced mutants are not GMOs, as there is no introduction of foreign hereditary material into induced mutant germplasm. Examples of key objectives of mutation in Thailand are to develop and characterize abiotic and biotic tolerant mutant germplasm and to breed disease resistant as new varieties with increased biotic tolerance. Plant breeding and genetic procedures usually start with mutation induction by irradiation or chemical mutagen and subsequently join force with other techniques such as tissue culture or molecular genetics.