Thailand's geography breaks into four main landscapes: forested mountain ranges and river valleys in the north, the low, sandy Khorat Plateau in the northeast, the flat rice-growing Central Plain drained by the Chao Phraya, and a long, narrow southern peninsula with the Andaman Sea on one side and the Gulf of Thailand on the other. The country covers 513,120 km², runs about 1,650 km from north to south, and its highest point is Doi Inthanon at 2,565 m.
An Elephant's Head on the Map: Shape, Size and Borders
Thai schoolchildren learn that their country looks like an elephant's head. The broad "head" is the mainland block of the north, northeast and centre; the "trunk" is the peninsula hanging south towards Malaysia. At its widest the head spans roughly 780 km from the Myanmar border to the Mekong. The trunk is far thinner: in Prachuap Khiri Khan province the land between the Tenasserim Hills on the Myanmar border and the Gulf of Thailand narrows to only about 11–13 km.
At 513,120 km², Thailand is a little smaller than France and slightly larger than Spain. It borders four countries and has about 3,200 km of coastline split between two seas. Long stretches of the land borders follow physical features, such as the Mekong with Laos and the Dangrek escarpment with Cambodia.
The everyday division has four regions (North, Northeast or Isan, Central, South); the official six-region system also separates out the West and East. The sections below run roughly north to south.
The Northern Ranges and the Four Rivers
Northern Thailand is a set of parallel ridges running north to south, the southern end of the uplands that spread out of Yunnan and Myanmar's Shan Hills. From west to east the main ranges are the Daen Lao, the Thanon Thong Chai, the Khun Tan and the Phi Pan Nam. Doi Inthanon (2,565 m) stands in the Thanon Thong Chai range southwest of Chiang Mai, and its cool, mossy summit forest holds plants and birds found nowhere else in the country.
Between the ridges lie four river valleys, and these valleys are where northern towns grew up. The Ping flows past Chiang Mai, the Wang past Lampang, the Yom past Phrae and Sukhothai, and the Nan past Nan and Phitsanulok. All four flow south. The Wang joins the Ping and the Yom joins the Nan, and the two combined rivers meet at Nakhon Sawan to form the Chao Phraya. The Bhumibol Dam on the Ping and the Sirikit Dam on the Nan store their water for the dry season.
In the far north, around Chiang Rai and Chiang Saen, the rivers flow the other way, into the Mekong. The Golden Triangle, where the Ruak River enters the Mekong, is where Thailand, Laos and Myanmar meet. Heavy teak logging in these uplands ended when Thailand banned commercial logging in natural forests in 1989.
Isan and the Khorat Plateau
East of the Phetchabun Mountains the land changes completely. The Khorat Plateau covers most of Isan, about a third of Thailand's area. It is a tilted saucer of sandstone that is mostly between about 100 and 200 m above sea level. The Phetchabun and Dong Phaya Yen ranges form the western rim, and the Sankamphaeng and Dangrek ranges form the southern one. The Preah Vihear temple, awarded to Cambodia by the International Court of Justice in 1962, sits on the edge of the Dangrek escarpment.
The plateau tilts gently to the southeast, and almost all of it drains through two rivers. The Chi, usually given as about 765 km, is often cited as the longest river entirely within Thailand. It joins the Mun just upstream of Ubon Ratchathani, and the Mun enters the Mekong at Khong Chiam. The low Phu Phan range divides this Khorat basin from the Sakon Nakhon basin to the north.
The plateau's soils explain much of Isan's history. They are sandy and poor in nutrients, and under much of the plateau lie thick beds of rock salt that make some fields salty. The mountains to the west also cast a partial rain shadow during the southwest monsoon. Rain is uneven, and both droughts and floods are common. Farmers adapted by growing rain-fed glutinous and jasmine rice in bunded paddies. The once-barren Thung Kula Ronghai plain now grows some of the country's most valued Hom Mali jasmine rice. Isan holds roughly a third of Thailand's people but has long been its poorest region.
The Central Plain: The Chao Phraya's Rice Delta
From Nakhon Sawan the Chao Phraya runs about 372 km south to the Gulf of Thailand at Samut Prakan. It crosses one of the flattest and most fertile landscapes in Asia. The upper plain is an old floodplain. Below the Chao Phraya Dam at Chai Nat (1957) the river splits into channels, and the Tha Chin branches off to the west, so the lower plain is a true delta of clay laid down by floods. The Pa Sak joins at Ayutthaya, the old capital, which sits on an island where three rivers meet.
This is Thailand's rice bowl and political core, and 19th-century canals (khlong) turned the delta into a grid of irrigated paddies. You can follow the river from source to sea in our guide to the Chao Phraya River.
Being flat and low has costs. Most of Bangkok lies only 1–2 m above sea level. In the 1980s, heavy pumping of groundwater made parts of the city sink by up to about 10 cm a year. Pumping controls have slowed this, but the risk remains: the 2011 floods affected 65 of 77 provinces, killed more than 800 people and swamped the industrial estates around Ayutthaya, with World Bank-estimated damage and losses of about US$46 billion.
The Western Hills and the Eastern Gem Coast
The West: Tenasserim Hills and Forest Corridors
The Tenasserim Hills (Thai: Tanaosri) run along the Myanmar border from Mae Hong Son down into the peninsula. In Kanchanaburi the Khwae Noi and Khwae Yai rivers cut through them; the 1942–43 "Death Railway" followed the Khwae Noi towards the Three Pagodas Pass. The region holds the largest unbroken forests in mainland Southeast Asia. The Thung Yai Naresuan and Huai Kha Khaeng wildlife sanctuaries became a UNESCO World Heritage Site in 1991 and are a stronghold for tigers, wild elephants and banteng.
The East: Between the Gulf and the Cardamoms
East of Bangkok, the coastal plain of Chonburi, Rayong, Chanthaburi and Trat lies between the Gulf and the western edge of the Cardamom Mountains, which reach into Thailand around Khao Soi Dao. Its soils support durian and mangosteen orchards, and Chanthaburi has traded sapphires and rubies for over a century. Deep water near Bangkok made it the industrial coast: the 1980s Eastern Seaboard scheme built the Laem Chabang port and the Map Ta Phut petrochemical complex, fed by Gulf of Thailand gas.
Down the Peninsula: Two Coasts and Two Monsoons
South of the narrowest point near Prachuap Khiri Khan, the land reaches the Isthmus of Kra, where only about 44 km separates the Andaman Sea from the Gulf. Below the isthmus a granite backbone runs down the peninsula. The Phuket range follows the west side, and the Nakhon Si Thammarat range follows the east. Khao Luang (1,835 m), the highest peak in the south, rises in the eastern range.
The Andaman Coast
The west coast is a drowned coast, flooded as sea levels rose after the last ice age. Limestone towers that once stood over a dry plain now rise straight out of the sea. Phang Nga Bay, Krabi and the Phi Phi islands are the best-known examples, and mangroves fill the sheltered inlets. Phuket, at about 543 km², is Thailand's largest island. Its wealth first came from tin. On 26 December 2004 the Indian Ocean tsunami hit this coast. Thailand officially counted around 5,400 dead, and Khao Lak was among the worst-hit places.
The Gulf Coast
The east coast is smoother. It has long sandy beaches, spits and lagoons. Thale Sap Songkhla is Thailand's largest natural lake, a lagoon system of over 1,000 km² that is fresh at its northern end and brackish where it meets the sea at Songkhla. Offshore lie granite islands such as Ko Samui and Ko Tao.
The two coasts get their rain at different times. The Andaman side takes the full southwest monsoon from May to October, and Ranong, facing it directly, receives around 4,000 mm a year. The Gulf side is partly sheltered from that monsoon and gets its heaviest rain from October to December, when the northeast monsoon crosses the Gulf. Elsewhere Thailand has three seasons: hot (March–May), rainy (June–October) and cool (November–February). Our page on the climate of Thailand covers the regional rainfall in more detail. The humid peninsula is the country's rubber and oil-palm belt.
How Thailand's Layout Differs from Vietnam's
Thailand and Vietnam are both long countries, each roughly 1,650 km from north to south. Vietnam is a thin S-shaped strip, 331,000 km² in area and only about 50 km wide at its narrowest, in Quang Binh. Its long spine is the Annamite Range (Truong Son), with the narrow coastal plain on one side and Laos on the other. Thailand has a compact centre, with the Khorat Plateau and Central Plain giving it a broad lowland core, and its thin section is limited to the peninsula.
- Heartlands: Vietnam has two deltas, the Red River delta around Hanoi and the Mekong Delta around Ho Chi Minh City, about 1,100 km apart and linked by a thin coast. Thailand has a single delta, the Chao Phraya's, at its centre.
- Height: Vietnam's Fansipan (3,143 m) is almost 600 m higher than Doi Inthanon.
- The Mekong: Thailand meets the Mekong as a border river with Laos. Vietnam gets the river's mouth: a delta of roughly 40,000 km² that is threatened by sinking land and salt water moving inland.
- Coasts: Vietnam's 3,260 km coast faces the South China Sea and its typhoons; Thailand's two coasts are largely sheltered from them.
Southward, the peninsula's granite ranges and tin belt simply continue into Malaysia as the Titiwangsa Range. For the cultural and economic sides of the Thai–Vietnamese pairing, see our Thailand vs Vietnam comparison.