UNCLOS 1982 specifies the width of its territorial sea up to a limit not exceeding 12 nautical miles measuring from the normal baseline of a coastal state, shown as the yellow area in the figure. Territorial sea must be established based on the International Laws, is regarded as the sovereign territory of the coastal state. It means the sovereignty of a coastal state extends beyond its land territory and internal waters to an adjacent belt of sea, this sovereignty extends to the air space over the territorial sea as well as its underlying seabed and subsoil (UNCLOS Article 2(1) and (2)). However, the must accept the right of innocent passage of foreign ships (UNCLOS Article 17).
Maritime Zone of Thailand