A tentative correlation scheme for the tectono-stratigraphic units of Northern Thailand and those of Western Yunnsn (China) is proposed. We point out that a correlation between the Changning-Menglian belt in Western Yunnan and the Nan-Uttaradit zone in Northern Thailand (or and a "cryptic suture" in the Chiang Rai-Chiang Mai region) is unlikely, for it would demand a "suture" which cuts across a zone with high-grade metamorphics and granite intrusions (Doi lnthanon-Lincang unit).Therefore, the northern continuation of the Lampang region is situated in the Simao region of Yunnan,as indicated by a very similar development during Permian and Triassic (Lampang-Yunxian unit). The Nan-Uttaradit zone is considered to be the easternmost part of this unit, and its northern continuation should be traceable via Luang Prabang in Laos into the southeastern parts of the Simao basin. Here,however, outcrops of this unit have not yet been found. The same is the case with the Phetchabun unit which follows to the east. Both units are probably hidden under a thick cover of Mesozoic red beds. The whole region was characterized by a highly mobile tectonic development with alternating phases of compressional and extensional deformation.