A foreigner entering in Thailand for other reasons than tourism must apply for a Non-Immigrant Visa at a Royal Thai Embassy or Consulate before arrival. The initial visa is valid for 90 days and can be extended at the Immigration office in Thailand.
If an extension of stay is not granted, the foreigner will need to leave the country to apply for another Non-Immigrant Visa at a Thai Embassy or Consulate in their home country or in another country near to Thailand.

The Non-Immigrant Visa indicates the period during which the holder can enter Thailand, not the length of time he is permitted to stay in the country. Permission to stay is indicated by the stamp put by the Immigration official in their passport, having the date by which they must exit the country.

Those holding a Non-Immigrant Visa and wishing to travel outside of Thailand must obtain a single or multiple re-entry permit before departing, otherwise the visa will not be valid when they try to re-enter Thailand.

There are several categories of Non-Immigrant Visas which include:

Education Visa
Pursuant to the Immigration Act, foreigners are permitted to enter the Kingdom for temporary stay for the purpose of education.
Those who are outside of Thailand can apply for a Non-Immigrant Education Visa at the Royal Thai Embassy or Consulate in that country.
Those who are already in Thailand and have a Non-Immigrant Dependent Visa, a Tourist Visa or a different type of visa can apply for a visa conversion to an Education Visa at the Immigration Department in Thailand.
The visa is valid for 90 days. If it is deemed necessary to stay in the Kingdom for a longer period, permission may be requested within at least 15 days before the expiry date at the Immigration Department.

Marriage Visa
In order to obtain a Marriage Visa, a foreigner must be legally married to a Thai national and able to evidence a minimum amount of 400,000 Baht in his personal bank account in Thailand or having an ongoing monthly income of no less than 40,000 Baht.
This does not apply for a foreign woman who marries a Thai citizen, but he must produce proof of payment of personal income tax.
A foreigner can apply for a work permit under privileged conditions, based on this type of visa instead of the Business Visa. For such work permit, a capital of 1 million Baht and 2 Thai staff must be employed.

Dependent Visa
Family members of foreigners who are in Thailand on long-stay visas may qualify for Non-Immigration O-type Visas. A Dependent Visa is applicable to the foreigner’s immediate family, including spouse, minor children, and parents. They will obtain a Dependent Visa once the foreigner’s Business Visa and work permit are issued.
A Dependent Visa can also be applicable if the foreigner holds a Retirement Visa and the spouse of the visa holder is younger than 50 years of age.
Supporting documents include evidence of relationship such as marriage certificates, birth certificates which should be certified as genuine by the applicant’s Embassy in Thailand.
The period of validity of the Dependent Visa is linked to that of the main visa holder’s length of stay.

Investment Visa
Non-Immigrant Investment and Business (IB) Visa is issued to foreign citizens employed by an investment projects which operate under the Investment Promotion Act, including the Thailand Board of Investment (BOI) and the Industrial Estate Authority of Thailand (IETA).
Foreigners must make an investment in Thailand with a value of at least 10 million Baht. The applicant should be able to evidence the said amount being transferred to their bank account in Thailand and provide official documents for the investment. The Investment Visa is in principle valid only for 90 days and has to be used within 3 months after receipt. A multiple re-entry visa is valid for one year and can in any case be extended as long as the investment is maintained.

In order to facilitate and speed up the process of issuing visas and work permits, the Thai government has established a One Stop Service Center for Visas and Work Permits where applications, once all relevant paper work are in place, can be processed in a few hours.

Retirement Visa
The Retirement Visa is available to foreigners aged 50 years or older, with satisfy basic health requirements and who have sufficient financial means to retire in Thailand. The application for the Thai Retirement Visa can be filed in his country of residency or in Thailand.
To qualify for the retirement visa in the first year, the holder needs to have a Thai bank account and obtain a bank statement which proves that a balance of at least 800,000 Baht has been deposited at least 60 days before the application. Alternatively, he is also eligible if he has an income or pension of at least 65,000 Baht per month which must be certified by the foreigner’s Embassy or Consulate in Thailand. Combinations of these two options are possible, too.

Employment is strictly prohibited. The Visa is usually valid for one year and the holder of the Retirement Visa is allowed to enter or leave the country as often as he like during the duration of the visa if he obtains a multiple re-entry permit.

In order to renew the Retirement Visa in the next year, the bank statement should state that funds have been held on the account for at least 3 months at the time of the application. Alternatively, the holder is also eligible if he can prove that he has a monthly pension or income throughout the year. A certification by the Embassy or Consulate will not be required in this case.

Retirement Visa (Long-stay Visa)
Since 21st August 2017, the Retirement Visa can alternatively be issued for an initial period of 5 years and renewable for an additional 5 years.

In this case the applicant must:
• Be at least 50 years of age and must not be prohibited from entering the Kingdom
• Not have a criminal record in Thailand or in his country of nationality or residence
• Have nationality or permanent residence in the country in which the application is submitted
• Not suffer from leprosy, tuberculosis, drug addiction, elephantiasis, or tertiary syphilis
• Have a deposit of at least 3 million Baht in a bank account, which amount must be maintained for at least one year after receiving the visa. After, the applicant must not withdraw more than 50% of that sum in the 2nd-5th year
• Have health insurance with a Thai insurance broker coverage for a minimum of 1 year equivalent to 1,000 USD for outpatient treatment and 10,000 USD for inpatient treatment
• Report to the Thai Immigration Bureau once every 90 days

The foreigner is required to apply for a 3-month NON-O X Visa at the Thai Consulate/Embassy aboard, or if a tourist is traveling with a different visa he can change this type of visa to NON-O X Visa. After that they may apply for an extension. Employment is strictly prohibited.

The target group for this visa are those from Australia, Canada, Denmark, France, Finland, Germany, Italy, Japan, Norway, Sweden, Switzerland, the Netherlands, the United Kingdom, and the United States.