Citizens of most countries require valid visa to enter Thailand. The Consulate General determines the duration of stay upon receiving an application.
Business Visa
Strictly speaking, there is no Thai visa that is officially termed as a short-term Thai business visa. However, the ‘ED’ study visa essentially serves the same purpose, granting holders visa the right to participate in projects or seminars and attend conference or training courses.
Thai ED visas are valid for a period of 90 days, with single entry and multiple-entry visas valid for 3 months, and multiple-entry visas for 1 year respectively.  However, the holder is not permitted to be employed in any capacity during their time in Thailand.
Tourist Visa
Thai tourist visas are granted for a period of 30 days, as a standard.  However, should an applicant be a national from a short-list of 40 countries (including the UK and USA), then their Thai tourist visa will be granted for a period of 60 days.
Additionally, the Thai tourist visa does not allow the visa holder to engage in any kind of employment in Thailand during their stay.