Cleavage folding, flexure folding, and intrusion of granite sills in Cambrian and Ordovician-Silurian sediments are a result of the 'Langkawi folding phase'. This folding phase is dated as late Silurian-Devonian in age. A subphase can be discerned which has caused a deformation of the slaty cleavage in the areas showing slight regional metamorphism and a cross-folding in the areas which have only suffered flexure folding. The presence of an unconformity between Silurian and Carboniferous strata in Thailand and the presence of only a few scattered outcrops of Devonian strata in Malaya suggest that the Langkawi folding phase was not only active in the Langkawi islands but must have had a wider sphere of influence. A low-angle overthrust has been developed during post-Permian and pre-granitic time. This thrust is later arched by the granite intrusion during the Pacific orogeny.