With mountains, hill-tribes and culture from Myanmar and China and provinces Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Lamphun, Lampang, Phrae, Uttaradit, Tak, Sukhothai, Phitsanulok, Kamphang Phet, Phichit, Phetchabun, Uthai Thani and Nakhon Sawan. Making a total of 17 provinces.
North-East Thailand (also called Isan)
With the khorat plateau, famous as being the rice-barn of Thailand and provinces Nakhon Ratchasima, Buriram, Si Saket, Surin, Ubon Ratchathani, Kalasin, Loei, Mukdahan, Nakhon Phanom, Bung Khan, Nong Bua Lamphu, Nong Khai, Sakhon Nakhon, Udon Thani, Amnat Charoen, Chaiyaphum, Khon Kaen, Maha Sarakam, Roi Et and Yasothon. Making in total 20 provinces.
The economic center of Thailand with industry and rivers and provinces Ratchaburi, Samut Songkhram, Samut Sakhon, Nonthaburi, Bangkok, Samut Prakhan, Kanchanaburi, Nakhon Pathom, Pathum Thani, Nakhon Nayok, Saraburi, Ayutthaya, Suphanburi, Ang Thong, Chainat, Lopburi and Sing Buri. It is a bit weird because Bangkok is not really a province and sometimes the term "Greater Bangkok" is used and this includes provinces like Nonthaburi and Samut Prakan. And some times Phetchaburi is included in "Central Thailand", but sometimes it is included in "South Thailand". Making a total of 17 provinces.
With Thailands chemical- and car industry, but also Pattaya, Koh Samet, Koh Chang and Koh Mak and provinces Chachoengsao, Chonburi, Rayong, Chantaburi, Trat, Sa Kaeo and Prachinburi. Making a total of 7 provinces.
With palm plantations but also Koh Samui, Krabi, Koh Tao and Patong and provinces Phetchaburi, Prachuap Khiri Kan, Chumphon, Ranong, Phang Nga, Surat Thani, Phuket, Krabi, Nakhon Si Tammarat, Trang, Phatalung, Satun, Songkhla, Pattani, Yala and Narathiwat. Sometimes Phetchaburi province is included in "South Thailand" or in "Central Thailand". Making a total of 16 provinces.
BTW weather-wise it might be a good idea to split South Thailand in East-Coast (Gulf of Thailand) and West-Coast (Andaman Sea).