A line joining Pedropunt, the northernmost point of Sumatra (5°40′N 95°26′E / 5.667°N 95.433°E / 5.667; 95.433), and Lem Voalan, the southern extremity of Goh Puket [Phromthep Cape on Phuket Island] in Siam [Thailand] (7°45′N 98°18′E / 7.750°N 98.300°E / 7.750; 98.300).

A line joining Tanjong Piai (Bulus), the southern extremity of the Malay Peninsula (1°16′N 103°31′E / 1.267°N 103.517°E / 1.267; 103.517), and The Brothers (1°11.5′N 103°21′E / 1.1917°N 103.350°E / 1.1917; 103.350), and thence to Klein Karimoen (1°10′N 103°23.5′E / 1.167°N 103.3917°E / 1.167; 103.3917).

The northeastern coast of Sumatra as far to the eastward as Tanjong Kedabu (1°06′N 102°58′E / 1.100°N 102.967°E / 1.100; 102.967), thence to Klein Karimoen.Early traders from Arabia, Africa, Persia, and southern India reached Kedah before arriving at Guangzhou.

Kedah provided accommodations, porters, small vessels, bamboo rafts, elephants, as well as tax collections for goods to be transported overland toward eastern ports of the Malay Peninsula such as Langkasuka and Kelantan.

In the 7th century, the maritime empire of Srivijaya, based in Palembang, Sumatra, rose to power, and its influence expanded to the Malay Peninsula and Java.

By launching a series of conquests and raids on potential rival ports on both sides of the strait, Srivijaya ensured its economic and military domination in the region, which lasted about 700 years.

The Strait of Malacca is part of the Maritime Silk Road that runs from the Chinese coast towards the southern tip of India to Mombasa, from there through the Red Sea via the Suez Canal to the Mediterranean, there to the upper Adriatic region to the northern Italian hub of Trieste with its rail connections to Central Europe and the North Sea.

[12] About a quarter of all oil carried by sea passes through the strait, mainly from Persian Gulf suppliers to Asian markets.

[13] In addition, it is also one of the world's most congested shipping choke points because it narrows to only 2.8 km (1.5 nautical miles) wide at the Phillip Channel (close to southern Singapore).

[13] The draught of some of the world's largest ships (mostly oil tankers) exceeds the Strait's minimum depth of 25 metres (82 feet).

[19] Thailand has developed plans to divert much of the strait's traffic and hence some of its economic significance to a shorter route: the Thai government has several times proposed cutting a canal through the Isthmus of Kra, saving around 960 kilometres (600 mi) from the journey between the two oceans.