The Maha Sarakham Formation potash deposit on ThailandLaos Khorat Plateau is one of the largest potash deposits in the world. Comprehensive studies show that the formation formed in late Cretaceous and was derived from seawater. Probably the formation formed in a continental setting and was a set of the “seawater-derived but terrestrial” deposits. The water-rock/salt reactions  happened not only during sedimentary process but also after postdeposition. The postdepositional potash deposits were  often reworked by these reactions. Occurrence of tachyhydrite is one of the characteristics of “abnormal evaporites” in this area and the formation of the mineral probably was related to the metamorphism of Cretaceous seawater. The forming mechanism of tachyhydrite can not be well understood until today. The relationship between Menyejing formation in LanpingSimao Basin and Maha Sarakham Formation on Khorat Plateau.is very close and there are some common characteristics in two formations. But there has been much controversial in some problems such as age, comparison of saltforming periods, etc. Finally, aiming at the future studies of potash deposits in this area, some new ideas and methods are put forward.