There are two main types of Non-Immigrant visas – multiple-entry visas, which are valid for multiple visits to Thailand within one year of issue; and single-entry visas, which are valid for one entry only during a period of 90 days.
The period of the visa does not give the holder the right to stay in Thailand for that period – that privilege is conferred by the Immigration Police on arrival. Most Non-Immigrant visa holders are granted an initial stay of 90 days.
Anyone wanting to do business or to work in Thailand requires a Non-Immigrant “B” visa.