Sundaland, the continental core of SE Asia, is a heterogeneous collage of continental blocks and volcanic arcs bounded by narrow suture zones that represent the remnants of ancient ocean basins. All the continental blocks of Sundaland were derived directly or indirectly from the Arabia-India–Australia margin of eastern Gondwana by the opening and closure of three successive ocean basins, the Palaeo-Tethys (Devonian-Triassic) Meso-Tethys (Permian-Cretaceous) and Ceno-Tethys (Jurassic-Cretaceous), and assembled by the closure of these ocean basins. Core Sundaland comprises a western Sibumasu block and an eastern Indochina–East Malaya block with an island arc terrane, the Sukhothai Island Arc, sandwiched between. The Palaeo-Tethys is represented by the Changning–Menglian, Chiang Mai-Chiang Rai, Chanthaburi and Bentong–Raub Suture Zones that form the boundary between Sibumasu and the Sukhothai Arc. The Indochina block was derived from Gondwana in the Devonian when the Palaeo-Tethys opened. The Sukhothai Arc formed on the margin of Indochina in the Carboniferous, and then separated by back-arc spreading in the Permian. The Jinghong, Nan–Uttaradit and Sra Kaeo Sutures represent this closed back-arc basin. The Sibumasu Terrane separated from Gondwana in the late Early Permian when the Meso-Tethys opened and collided with the Sukhothai Arc and Indochina in the Middle-Late Triassic. The Cathaysian West Sumatra block possibly represents a part of the Sukhothai Arc and was emplaced by strike-slip tectonics outboard of Sibumasu in the Triassic. The West Burma Block was already attached to Sundaland before the Late Triassic and is likely a disrupted part of Sibumasu. East Java-West Sulawesi and South West Borneo are tentatively identified as the missing 'Argoland' and 'Banda' blocks which must have separated from NW Australia in the Jurassic and subsequently accreted to SE Sundaland in the Cretaceous.