Thai Visa
Basic Requirements 
Most international travellers wishing to gain entry to Thailand need to obtain a Thai visa.  However, visitors from a number of visa-exempt countries can travel to Thailand for tourism purposes without having a Thai visa.  These countries include the UK and the USA.
Please note: Each individual visit made to Thailand by a visa-exempt traveller can only be up to 30 days in length, with the maximum limit for combined visits to Thailand being 90 days every 6 months.  Should a visitor from a visa-exempt country wish to visit Thailand on a single trip with a length of up to 60 days, they must apply for the Thai tourist visa.
Processing Times
The processing time for a Thai visa is subject to change.  A Thai visa’s processing time depends very much on the type of visa, the nationality of the person applying, the time of year and other variables.  Therefore, it is advised that applicants start the application process well in advance of their scheduled trip.
Temporary Thai Visas
Thai Tourist Visa
Applicants for the Thai tourist visa must meet all the necessary requirements, including having a current and valid passport. Visitors must also show evidence of sufficient funds for the duration of their stay in the country.
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.
Thai Business Visa
Strictly speaking, there is no Thai visa which 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.
To apply for this visa, applicants are required to show evidence of their purpose, such as a letter of invitation from the business they will be visiting in Thailand. Additionally, they must be properly certified to visit by the appropriate government agency in Thailand.
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.
Thai Embassy Information
Royal Thai Embassy London 
29-30 Queens Gate
Telephone:  020 7589 2944
Fax:  020 7823 7492
Website:  Source: