Laos–Thailand border

The border starts in the north at the tripoint with Myanmar at the confluence of the Kok and Mekong rivers, following the latter towards the south-east.[2] It then leaves the river and proceeds overland in a broadly southwards direction over various hill ridges, down to the Hueang River. It then follows this river to the north-east up to the confluence with the Mekong, from where it follows the Mekong for the majority of the border's length. Just north-west of Pakse the border leaves the Mekong and then follows the ridge of the Dângrêk Mountains south the tripoint with Cambodia.[2]

A pillar marking the border (2002)

From the 1860s France began establishing a presence in the region, initially in modern Cambodia and Vietnam, and the colony of French Indochina was created in 1887.[2] The Lao kingdoms were at this point tributary states of the Kingdom of Siam (the old name for Thailand), however all areas east of the Mekong were annexed to French Indochina in 1893 following the Franco-Siamese War.[2][3][4] In 1902 Siam was forced to cede areas west of the Mekong to France, encompassing the modern province of Sainyabuli and the western half of Champasak Province.[2][4] More land was ceded in another treaty in 1904, and again in 1907.[2][4] A minor treaty in 1926 cleared up the outstanding issue of sovereignty over islets in the Mekong.[2] Following Japan’s invasion of French Indochina in 1940 the ceded areas west of the Mekong and south-western Laos were returned to Thailand, however this arrangement was annulled following Japan's defeat and the pre-war border reinstated.[2]

Laos obtained a partial independence from France in 1949, gaining complete independence in 1953, with the boundary then becoming one between two sovereign states. Thailand occasionally made claims on the territories ceded to Laos during the colonial era, with tensions rising following the victory of the Communist Pathet Lao in the Laotian Civil War in 1975.[4] Friendship treaties were signed in 1976 and 1979 in attempt to calm tensions, with both sides recognising the territorial integrity of the other.[4][5] However fighting broke out in 1984 over disputed villages adjacent to the frontier in Sainyabuli Province/Uttaradit Province, and again in 1987–88 over a nearby area.[4] A joint committee was established in 1991 which aimed to resolved the dispute peacefully, however discussions dragged on throughout the decade.[4] A joint boundary commission was established in 1997, however its work was suspended in 1998 following the Asian financial crisis.[4] As of 2018 border demarcation is still ongoing.[6][7]

As of 2019, there were 20 permanent border crossings and 29 checkpoints for border trade.[8][9]

Permanent Border Crossing

No	Laos	Thailand		Notes
	Border post	Border post	Opening hours
1	Houayxay, Houayxay District, Bokeo	Chiang Khong Pier, Chiang Khong District, Chiang Rai	0800 - 1800	Ferry Border Crossing.
2	Mittaphab 4, Ban Don, Houayxay District, Bokeo	Chiang Khong, Chiang Khong District, Chiang Rai	0600 - 2200	Border across the Fourth Thai–Lao Friendship Bridge.
3	Tonpheung, Ton Pheung District, Bokeo	Chiang Saen Pier, Chiang Saen District, Chiang Rai	0800 - 1800	Ferry Border Crossing.
4	Golden Triangle, Ton Pheung District, Bokeo	Golden Triangle, Ban Sop Ruak, Chiang Saen District, Chiang Rai	0600 - 2000	Ferry Border Crossing.
5	Pang Mon, Khop District, Sainyabuli	Ban Huak, Phu Sang District, Phayao	0600 - 1800
6	Ban Nam Ngeun, Ngeun District, Sainyabuli	Ban Huai Kon, Chaloem Phra Kiat District, Nan	0800 - 2000
7	Pha Keo, Parklai District, Sainyabuli	Phu Doo, Ban Khok District, Uttaradit	0600 - 2000
8	Nam Hueang, Kenethao District, Sainyabuli	Ban Na Kraseng, Tha Li District, Loei	0700 - 1800	Border across the Nam Hueang Thai–Lao Friendship Bridge.
9	Kenethao, Kenethao District, Sainyabuli	Ban Pak Huai, Tha Li District, Loei	0800 - 1800	Ferry Border Crossing.
10	Xanakharm, Xanakharm District, Vientiane Province	Chiang Khan, Chiang Khan District, Loei	0800 - 1800	Ferry Border Crossing.
11	Ban Wang, Xanakharm District, Vientiane Province	Ban Khok Phai, Pak Chom District, Loei	0800 - 1600	Ferry Border Crossing.
12	Tha Dua, Hadxayfong District, Vientiane Prefecture	Tha Sadet, Mueang Nong Khai District, Nong Khai	0800 - 1800	Ferry Border Crossing.
13	Mittaphab 1, Ban Dongphosy, Hadxayfong District, Vientiane Prefecture	Nong Khai, Mueang Nong Khai District, Nong Khai	0600 - 2200	Road and Railway Border Crossing.Border across the First Thai–Lao Friendship Bridge. Train services operational between Nong Khai railway station and Thanaleng railway station.
14	Pakxan Pier, Pakxan District, Bolikhamsai	Bueng Kan Pier, Mueang Bueng Kan District, Bueng Kan	0800 - 1800	Ferry Border Crossing.
15	Thakhek, Thakhek District, Khammouane	Nakhon Phanom Pier, Mueang Nakhon Phanom District, Nakhon Phanom	0600 - 1800	Ferry Border Crossing.
16	Mittaphab 3, Thakhek District, Khammouane	Nakhon Phanom, Mueang Nakhon Phanom District, Nakhon Phanom	0600 - 2200	Border across the Third Thai–Lao Friendship Bridge.
17	Xayaphoum Pier, Kaysone Phomvihane District, Savannakhet	Mukdahan Pier, Mueang Mukdahan District, Mukdahan	0600 - 1800	Ferry Border Crossing.
18	Mittaphab 2, Kaysone Phomvihane District, Savannakhet	Mukdahan, Mueang Mukdahan District, Mukdahan	0600 - 2200	Border across the Second Thai–Lao Friendship Bridge.
19	Paktaphan, Lakhonepheng District, Salavan	Ban Pak Saeng, Na Tan District, Ubon Ratchathani	0800 - 1800	Ferry Border Crossing.
20	Vang Tao, Phonthong District, Champasak	Chong Mek, Sirindhorn District, Ubon Ratchathani	0600 - 2000

Laotian and Thai boundary markers

Checkpoint for Border Trade

Border crossing open for cross-border local trade only. There are 29 checkpoints for border trade officially recognized by the Ministry of Interior, located in provinces. Entering the opposite country beyond these checkpoints and their associated markets is illegal.

The First Thai-Lao Friendship bridge

• Laos–Thailand relations