If you are going to be working in Thailand, you are going to need to obtain a Thai business visa in order for the labour department to process your work permit. Even though you may apply for a work permit to work in your own business, there are work permit restrictions with regards to foreigners working in Thailand and what type of trades they be involved in.
You need to apply for a “B” or business visa before coming to Thailand to work. This visa is usually single entry and valid for 3 months alternatively it can be a multiple entry visa which has four entries and valid for 1 year. The “B” visa does not give you the right to work in Thailand as you must still apply for a work permit or what expats call a working visa .
Once you enter Thailand the immigration official will stamp your passport for 90 days. During this 90 day period you need to apply for a work permit at the labour department. Speak to an attorney with regards to what is required as the process is becoming more complex with each passing year. The labour department will issue you with a work permit and the immigration department will then extend your visa to whatever the date of expiration on your work permit is. If you are hired for one year and your work permit if for one year, Thai Immigration will extend your visa for one year to expire with the expiration of your work permit.
Speak to an attorney in Thailand with regards to work permits and “B” or Business visas as the process as stated before is become more complex with changing rules and more restrictions.