The region experienced complicated tectonics during the Paleozoic, long-running shallow water conditions and then renewed uplift and erosion in the past several million years ago.
Early Paleozoic rocks are only known in western Thailand, such as sandstones on Tarutao Island in the Andaman Sea with Cambrian and Ordovician trilobite fossils.
Volcanic activity was common in the Devonian and Carboniferous as limestone accumulated on a western facing continental margin (exposures of these rocks are visible at Petchabun-Loei in east-central Thailand).
Some geologists have interpreted pebbly diamictite mudstone and turbidites in the Mergui Group as glacial sediments, with possible origin in India or northwest Australia.
Along the western edge of the Khorat Plateau, a limestone dominated shelf sequence abuts turbidites and pyroclastic flow deposits.
A magmatic arc around a west-dipping subduction zone produced intermediate and felsic volcanic rocks in the north around Lampang to the east of Chiang Mai.
With calc-alkaline volcanic rock at its base, the Khorat Plateau is diachronous giving the appearance that basin deposition moved further west through the Mesozoic.
Typically, they are small and isolated with biotite and muscovite-rich granite as well as potassium feldspar megacrysts, hornblende and large mica-tourmaline or lepidolite pegmatites.
For much of the Cenozoic, Thailand was comparatively flat until rapid uplift began in the north, accompanied by block faulting and horst and graben formation in the Pliocene and Pleistocene, leaving valley floors to fill with gravel and sand.
Large quantities of natural gas and some petroleum have been found in the blended terrestrial and marine sedimentary strata along the Andaman Sea coast, ranging in age from Oligocene to Pliocene.
Based on aerial magnetic surveys and boreholes, geologists have inferred that the Chao Paya Basin is believed to be a composite graben with uneven underlying topography.
Cassiterite is found in quartz veins, skarn deposits, aplite, pegmatite and greisenized granite intrusions, often with accessory minerals such as fluorite, muscovite, wolframite, columbite, tantalite, tourmaline, topaz, zircon and beryl.
Additionally, Thailand has some production of gypsum, limestone, kaolin, sapphire, zircon, tantalite, columbite, antimony, lead, zinc, barite and fluorite.