You can have a change of visa status in Thailand without the need to leave the country. Its not very common but there are those expats who change visa status from time to time. This as they work then dont work. The most common one are those who have a marriage visa for Thailand. Then got work and have their visa status changed because of the work permit. There are also those who arrive on a tourist visa and then get married or decide to retire.
Change of Visa Status
Convert tourist visa to retirement visa
Many people arrive in Thailand on a tourist visa to see where they would like to live. This or if they wish to live in Thailand. Many times they will arrive on a tourist visa and look for a good location. When they find a good location they will want to convert a tourist visa to a retirement visa. This is very common. Having said that however like all Thai visa status changes. You will need to decide before the 60 day visa expires. The visa conversion in Thailand takes about 30 days.
Before your 60 day tourist visa expires. You apply for an extension of the tourist visa. This is done on the TM.7 form which you can download here. For 1,900 THB they will give you an additional 30 days. Once it is extended then hand the passport back again. Then have that 30 day additional visa extension converted to your retirement visa. By the time your 90 day retirement visa comes close to expiration. The deposit in your Thai bank would have matured by then for the (time in bank) financial requirements of the retirement visa. Remember that the new retirement visa gives you 90 days from when it was converted. See also the Thai work permit cost in the country.
Convert tourist visa to marriage visa
Much like those who retire in Thailand. Many arrive in Thailand on a 60 day tourist visa. They then get married and now they have to complete a change of visa status. Converting the tourist visa to a marriage visa. The process is the same as the retirement visa. Yes, the same extension of the tourist visa at 30 days will also allow you an additional 90 days from the start of the marriage
visa. This allows you time to meet the financial requirements of the marriage visa in Thailand. This as by the time the 90 days comes to extend the visa for one year. The time deposit at the bank will have met the current immigration requirements.
You can search this website for more information and guidance. you can have the visa conversion done at any immigration office. This from the large Thai immigration in Bangkok all the way to Thai immigration in Chachoengsao and immigration in Phuket. See the side bar for more details and direction.
See also the issues with regards to the visa waiver or visa on arrival when you are considering Thailand as a backpacker destination.