The local climate is tropical and characterized by monsoons. There is a rainy, warm, and cloudy southwest monsoon from mid-May to September, as well as a dry, cool northeast monsoon from November to mid-March. The southern isthmus is always hot and humid.
Thailand is home to several distinct geographic regions, partly corresponding to the provincial groups. The north of the country is mountainous, with the highest point being Doi Inthanon at 2,565 metres (8,415 ft) above sea level. The northeast, Isan, consists of the Khorat Plateau, bordered to the east by the Mekong River. The centre of the country is dominated by the predominantly flat Chao Phraya river valley, which runs into the Gulf of Thailand. The south consists of the narrow Kra Isthmus that widens into the Malay Peninsula. Politically, there are six geographical regions which differ from the others in population, basic resources, natural features, and level of social and economic development. The diversity of the regions is the most pronounced attribute of Thailand's physical setting.
The Chao Phraya and the Mekong River are the sustainable resource of rural Thailand. Industrial scale production of crops use both rivers and their tributaries. The Gulf of Thailand covers 320,000 square kilometres (124,000 sq mi) and is fed by the Chao Phraya, Mae Klong, Bang Pakong and Tapi Rivers. It contributes to the tourism sector owing to its clear shallow waters along the coasts in the Southern Region and the Kra Isthmus. The Gulf of Thailand is also an industrial center of Thailand with the kingdom's main port in Sattahip along with being the entry gates for Bangkok's Inland Seaport. The Andaman Sea is regarded as Thailand's most precious natural resource as it hosts the most popular and luxurious resorts in Asia. Phuket, Krabi, Ranong, Phang Nga and Trang and their lush islands all lay along the coasts of the Andaman Sea and despite the 2004 Tsunami, they continue to be and ever more so, the playground of the rich and elite of Asia and the world.
Plans have resurfaced of a logistical connection of the two bodies of water which would be coined the Thai Canal, analogous to the Suez and the Panama Canal. Such an idea has been greeted with positive accounts by Thai politicians as it would cut fees charged by the Ports of Singapore, improve ties with China and India, lower shipping times and increase ship safety owing to pirate fears in the Strait of Melaka and, support the Thai government's policy of being the logistical hub for Southeast Asia. The ports would improve economic conditions in the south of Thailand, which relies heavily on tourism income, and it would also change the structure of the Thai economy moving it closer to a services center of Asia. The canal would be a major engineering project and has expected costs of 20–30 billion dollars.