The non immigrant "B" or Business Visa is available to those who wish to enter Thailand for the purposes of conducting business or seeking employment. There is are a few options with regards to the Thai Business Visa. Normally the Thai embassies will only issue you with a 3 month / 90 day Business Visa as this is all that would normally be required for starting Thai Work Permit process. The "B" Visa does not give you the right to work in Thailand as this is commonly misunderstood.
The "B" Visa is therefore not a Work Visa as some one refer to it as there is no such visa called a Thai work visa. The"B"visa or Thai business visa is correct visa to start the work permit process, however is not a valid document for holding employment on its own. At times the embassies might issue you with a Multiple Entry "B" Visa. These would normally be a one year Multiple Entry "B" Visa which is valid for a year and made of 4 visa 'legs'. The one year Thai "B" Visa is divided into 4 legs. Each leg is valid for 3 months (90 days). Every 90 days you have to leave Thailand and return to activate the next leg. This is commonly called a Visa Run and is rather common in Thailand.
When applying for a Thailand "B" Visa you would need a letter from your prospective employer requesting the visa on your behalf so that they may apply for a work permit for you. This letter, on the official letterhead of the business you would hand in with your application form.
1. The letter must be addressed to the appropriate Embassy;
2. They should introduce the applicant, being you and state the specific nature of business;
3. Contact details of the applicant in the country, and the company;
4. Guarantee of financial support for the applicant must be stated;
5. The letter must -- i.e.; XYZ Company guarantees financial responsibility for Mr. Smith;
6. The letter must be signed by someone other than the applicant;
Should you need further information, contact any of the 7 offices of Law Firm International in Thailand, or the US or UK office.
Note : If you are applying for a position as a teacher you will need to also submit a resume, copy of your qualifications and a teacher license if you already have one. You also need to provide a police clearance certificate when you apply for the visa for teaching. Normally the school will also give you a letter from the MOE to show that you can teach in Thailand.