Nine fossil wood samples from the Mesozoic bedrock and the Quaternary terrace deposits of the Lower Mekong Basin in Southeast Asia including Thailand,Laos and Cambodia were investigated in order to assist in developing a hypothesis about the Mekong River palaeocourses. Six of the samples were conifers assigned to Aga-thoxylon sp.,and three were dicots of cf. Pahudioxylon sp. and two unknown taxa( Dicotyloxylon sp.).The preservation of two dicotyledonous wood samples is insufficient for precise identification to family level,such that the samples are not suitable with respect to investigation of the river palaeocourse. However,these findings increase the systematic data of the fossil wood from the Mekong Basin. Further investigations of fossil wood from the Mekong Basin are in progress to gain a regional perspective on the plant communities and to form better reconstruction of the palaeoenvironment. Nine fossil wood samples from the Mesozoic bed rock and the Quaternary terrace deposits of the Lower Mekong Basin in Southeast Asia including Thailand, Laos and Cambodia were investigated in order to assist in developing a hypothesis about the Mekong River palaeocourses. Six of the samples were conifers assigned to Aga-thoxylon sp., and three were dicots of cf. Pahudioxylon sp. and two unknown taxa (Dicotyloxylon sp.). The preservation of two dicotyledonous wood samples is insufficient for precise identification to family level, such that the samples are not suitable However, these findings increase the systematic data of the fossil wood from the Mekong Basin. better reconstruction of the palaeoenvironment.