Generally, a visa is required in Thailand; however, other nationalities are not required to apply for a tourist visa when visiting the country. In compliance with the new visa exemption list presented below, the following countries are eligible to enter Thailand without a visa through the land-border checkpoint for only twice a year. Entering the country through international airports will not be affected by this regulation.

Nationals of the following countries and territories are entitled to a 30-days visa exemption:

AUSTRALIA	AUSTRIA	BELGIUM	BAHRAIN
CANADA	CZECH REPUBLIC	DENMARK	ESTONIA
FINLAND	FRANCE	GERMANY	GREECE
HONG KONG	LIECHTENSTEIN	LUXEMBOURG	MALAYSIA
MONACO	THE NETHERLANDS	NEW ZEALAND	NORWAY
OMAN	PHILIPPINES	POLAND	PORTUGAL
QATAR	SINGAPORE	SLOVAK REPUBLIC	SLOVENIA
SPAIN	SOUTH AFRICA	SWEDEN	SWITZERLAND
TURKEY	UNITED ARAB EMIRATES	UNITED KINGDOM	UNITED STATES

Nationals from other countries and territories are required to obtain a visa in accordance with their purpose of visit. Delegates are advised to obtain a tourist visa. A tourist visa is a 60-day visit in the country. This can be extended up to another 30-days by means of a visa run. If you are planning to extend your visa, you can convert the visa to a non-immigrant visa which will require you to go to any nearby city or country such as Penang or Kuala Lumpur, Malaysia.

To learn more about obtaining a Thai visa, you can refer to the Thai Embassy's official guidelines with the link below:
http://www.thaiembassy.com/visa/thaivisa.php