The Malaysia-Thailand border consists of both a land boundary across the Malay Peninsula

Malay Peninsula

The Malay Peninsula or Thai-Malay Peninsula is a peninsula in Southeast Asia. The land mass runs approximately north-south and, at its terminus, is the southern-most point of the Asian mainland...

 and maritime boundaries in the Straits of Malacca and the Gulf of Thailand

Gulf of Thailand

The Gulf of Thailand , also known in to Malays as Teluk Siam literally meant Gulf of Siam, is a shallow arm of the South China Sea.-Geography:...

/South China Sea

South China Sea

The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...

. Malaysia lies to the south of the border while Thailand

Thailand

Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

 lies to the north. The Golok River

Golok River

The Golok River is a river that lies on the border between Malaysia and Thailand. It is spanned only by the Malaysian-Thai friendship bridge. The name of the river in Malay is Sungei Golok, meaning "River of Swords"....

 forms the easternmost 95 km stretch of the land border.

The land border is based on the 1909 treaty between Thailand, then known as Siam, and the British which started to exert its influence over the northern Malay states of Kedah

Kedah

Kedah is a state of Malaysia, located in the northwestern part of Peninsular Malaysia. The state covers a total area of over 9,000 km², and it consists of the mainland and Langkawi. The mainland has a relatively flat terrain, which is used to grow rice...

, Kelantan

Kelantan

Kelantan is a state of Malaysia. The capital and royal seat is Kota Bharu. The Arabic honorific of the state is Darul Naim, ....

, Perlis

Perlis

Perlis is the smallest state in Malaysia. It lies at the northern part of the west coast of Peninsular Malaysia and has Satun and Songkhla Provinces of Thailand on its northern border. It is bordered by the state of Kedah to the south...

 and Terengganu

Terengganu

Terengganu is a sultanate and constitutive state of federal Malaysia. The state is also known by its Arabic honorific, Darul Iman...

 in the early 20th century.