Thailand is one of modernizing countries in the mainland of Southeast Asia, with Bangkok Capital sitting at the mouth of the significant Chao Phraya River which is admired by Temple of Dawn or Wat Arun and richly emerges The Grand Palace that houses traditional Royal Buildings, temple of the emerald Buddha and other impressive architectures and arts.

It depends on from which country you take flight, the main popular international airports are Suvarnabhumi Airport, Phuket International Airport, Don Mueang International Airport, Chiang Mai International Airport, Mae Fah Luang International Airport in Chiang Rai and Samui International Airport in Koh Samui.

Border crossing is always available and convenient at some of main international borders between each country while others are still restrictive, involved with visa exempt, causing headache, obtaining visa and tedious visa process. You can fairly find public transportation, buses, train or private taxis at those borders and it is better that you should have your visa ready to avoid taking much time on visa processing.
• Thailand – Cambodia: Had Lek/Koh Kong, Ban Pakard/Pailin, Ban Laem/Duan Lem, Aranyaprathet/Poi Pet, Chong Jom/O’Smach, Chong Sa Ngam/Anlong Veng
• Thailand – Laos: Nong Khai/Vientiane, Mukdahan/Savarnakhet, Loei/Sayabouly, Nakhon Panom/Khammouane, Chiang Rai/Bokeo, Ubon Rathchathani/Champasak
• Thailand – Malaysia: Pedang Besar, Sadao/Bukit Kayu Hitam
• Thailand – Myanmar: Mae Sai/Tachileik, Mae Sot/Myawaddy, Ranong/Kawthaung
More detail: https://www.thaiembassy.com/thailand/thailands-land-borders

Who needs visa to Thailand?

Thai tourist visa fee cost $30 per entry which allows tourists to stay in Thailand for more than 30 days. However, visa exemption is permitted for a stay of 45-90 days in Thailand and its available for most of Asian (except Cambodia and Myanmar) countries included Australia and EU countries such as United State, Canada, France, England, Finland, Germany, Greece, Denmark, Italy, Span, Israel, Russia, Portugal, Qatar, Slovenia and more to enter Thailand without a visa but the visa exemption rule must meet their requirement while other 19 countries of passport holders can obtain visa on arrival at Thailand’s international airports, those countries include China, Cyprus, Ethiopia, Fiji, Georgia, India, Kazakhstan, Malta, Bulgaria, Bhutan, Papua New Guinea, Romania, Saudi Arabia, Taiwan, Uzbekistan, Vanuatu, Mexico, Nauru and Mauritius. You should apply for e-visa in advance if you plan to enter Thailand via land borders.
For Thai visa detail: https://www.thaiembassy.com/thailand-visa/thailand-tourist-visa