The travel requirements depends on the country where you come from.
By the end of 2018, France, the United Kingdom and the United Arab Emirates will be able to apply for a Thai eVisa.
It is also possible to make a request for an extension of your visa up to 90 days validity.
For travelers who will do a trip of less than 30 days, a visa tourist is not required.
Chinese citizens may request an EVisa Thailand, under certain conditions and specific travel periods.
Actually, Chinese citizens and other 22 other countries will only able to request a visa on their arrival in Thailand.
Travelers who are not from visa-exempt countries will need to apply online for an Thailand Evisa to be able to travel in Thailand.