Most foreign nationalities would like to stay in Thailand for a longer period. While they arrive in Thailand with the initial visa (such as tourist visa), if they wish to stay in Thailand for more than 30 days or if they are planning to come to Thailand and their purpose of visit is business, they can apply for a One year Thai visa or 90-day Thai visa.
One year non-immigrant Thai visa
You can apply for a 1-year multiple entry non-immigrant visa which will allow you to stay in Thailand and travel in and outside the country for 1 year. This one year thai visa is issued for applicants who wish to enter Thailand to perform official duties or religious activities, conduct business or investment, work, and study, visit the family and other activities. This type of visa can be extended for 3 months on or before the visa expiration date.
90 day Thai visa
If you intend to stay in Thailand for more than the normal tourist visa, the 90 day non-immigrant visa is the best option which will allow you to stay 90 consecutive days. 90 day non-immigrant visa to Thailand for foreign citizens is issued to applicants who wish to enter Thailand to perform official duties or religious activities, conduct business, work, and study, visit the family and other activities for a period of 90 days with the ability to extend their stay for 7 days.