Currently, nationals from 56 countries are able to get On-Arrival entry Visas into Thailand for 30 days and from 76 other countries, visas valid for 15 days. These may be obtained on arrival at any of the five international airports at Bangkok, Chiang Mai, Chiang Rai, Phuket and Hat Yai.
For longer stays you should apply for a Tourist Visa of 60 Days or a Non-Immigrant Visa of 90 Days, for business or other related other purposes, from any Thai Embassy or Consulate prior to Travel.
Please note that if you wish to work or stay in Thailand for any other reason longer than 90 days you need to obtain the relevant visa in Thailand. You require a Non-Immigrant visa to be issued first before you travel to Thailand. You can not/not apply for long term multiple entry visas or a work permit if you only hold a On-Arrival Visa or a Tourist Visa.
Non-Immigrant 90 day Visas can be issued for the following reasons but require appropriate supporting documentation from the sponsoring institutions or Agencies:-
Business, Conferences, Research, Teaching, Mass Media, journalists,
Investment,
Education,
Family Reunion,
Retirement,
Medical Treatment,
Special Reasons.
Non-Immigrant 365-day Visas can be issued only if your first hold a Non-Immigrant 90-day Visa. The 12 month Visa is issued as an extension to that visa on the following grounds:-
Business or Working Professionals,
Accredited Investors,
Those supporting Thai family, Spouses or Children,
Senior-Citizens retiring in Thailand.
The documentation required for the extension of your visa to a 365-day Multiple Entry Business Visa is considerable. You will need the following:-
Originals and certified copies of your birth certificates (including accompanied dependents),
Marriage certificate (for accompanying spouse)
Academic records, Trade qualifications, or Professional certificates,
Passport photos,
A letter from your company or sponsoring Institution stating nature of business, reason for employing you in the particular position in Thailand, your salary & Skills qualifications, and the number of Thai citizens your company or organisation employs.
Company Registration documentation, Balance sheets, Annual reports etc.
In addition to a Non-Immigrant Visa extension if you wish to work in Thailand you will also need to apply for a Work Permit. Up until last year, work permits were issued by the Ministry of Commerce. Under the revised Alien Business Operations Act they are issued by the Ministry of Labour. The documentation required for a Work Permit is as extensive as for the Visa. It is possible to arrange for both the Work Permit and the long term visa to issued at the One-Stop Shops set up by the Department of Immigration.
Our Strong Advice on the subject of Work Permits and Visas is that you get your Legal advisers to make the arrangements for you or that you seek assistance from your local Thai staff to do so. This process is traditionally very time consuming and highly procedural in nature. As you are legally only required to present yourself for identification purposes the rest can be done by someone who does have the time and patience to do so.