Any foreigner looking for entry to the Kingdom of Thailand for investment, medical treatment, study, mass media, business, employment, and religious or other purposes is required to apply for a visa from the Consulate General or the Thailand Embassy. A foreigner should have travel documents or a passport validated by the Royal Thailand Government. You must also comply with conditions implemented by the Immigration Act B.E.2522. The Royal Thai Consulate Generals and Royal Thai Embassies have the right to issue visas to a foreigner traveling in Thailand.

Thailand Immigration Laws

Under the Alien Employment Act, a foreigner cannot make any act of service or work unless the Ministry of Labor or the Department of Employment of Thailand issues a work permit in your name. This act also provides basis in deporting any illegal foreigner who works without a permit issued by Thailand immigration.

The Labor Protection Act of the Civil Commercial Code (CCC) is primarily responsible for managing the labor protection of immigrants who work and live in Thailand. These immigration laws of Thailand are focused on every aspect of the employees’ immigration concerns such as overtime wages, female and child labor, working hours, employee welfare, sick leave, employee social security, remuneration, and employee termination or resignation.

There are requirements in the application for a visa :

a) For foreigners:
  • Nationals of countries specified by the Ministry and approved by the cabinet. The nationality must be the same as the country issuing the passport
  • Entering Thailand as tourists for 15 days
  • 1 passport picture 4x6 cm, not more than 6 months old
  • No blacklisted person (persona non grata) according to the immigration laws
  • Confirmed onward or return ticket within 15 days
  • Indication of actual address of residence in Thailand
  • Cash of at least 10,000 Baht (US$ 250) per person or 20,000Baht (US$ 500 per family)
  • Valid passport with validity of at least 6 months

b) Application for visa on arrival:
  • Arriving passengers wishing to apply for a visa on arrival must fill in the application form (TM. 88) available at the Visa on arrival counter in terminals 1 and 2 at Bangkok International Airport.

The form TM 88 (formerly TR 15) together with the application fee of 1,000 Baht must be handed in at the Visa on arrival counter. The fee is payable in Thai Baht only. Currency exchange service is available at the bank counters near the Visa on arrival counters.

Types of Non-Immigrant Visas

Single Entry Visa

All types of visas allow a single entry visa in Thailand. It is valid for three months from the date of issuance and allows the visitor to enter Thailand with a single entry status. For an additional visit, foreigners will be required a new visa that may be acquired from the Thai Embassy or Consulate outside Thailand. This single entry visa can be extended for thirty days without necessarily leaving Thailand by applying for an extension at the Thailand Immigration office.

Multiple Entry Visa

Multiple entry visas are valid 12 months from the date of issuance. It allows you to enter Thailand on many occasions, and you are required to stay in Thailand for up to 90 days.  Multiple entry visas can be extended up to 15 months.

This experience was validated in Thailand Expat Forum last September 11, 2009:

I think there is no limit to how many times. Only how long you stay. You are limited to a maximum of 90 days in any 180 day period. So for you, this would mean 90 days max in Thailand.

Remember, you will only get 30 Days Visa Exemption Stamp if you arrive at Airport. Land arrivals receive only a 15 day stamp

Thai Work visa

If you want to work legally in the territory of Thailand, you must have a non-immigrant business visa and work permit. You should have a visa before applying for the work permit. If you intend to work in the Republic of Thailand, you also need to get the visa before actually arriving in Thailand. You must possess the work permit before you begin to work.

Retirement Visa

If you are over fifty years old and want to retire in Thailand, you should get a retirement visa. The requirement to obtain this retirement visa is a criminal clearance. This means you must not have any criminal record whatsoever. The local police should verify your clearance to acquire a form from them. A medical certificate from your physician is needed to check the presence for communicable diseases such as TB and AIDS.

Official or Diplomatic Visa

The Embassies and Consulate Generals of Thailand may grant visas to officials or diplomatic passport holders who want to assume duties at the foreign Consulate or Diplomatic Mission or International Organization in the kingdom of Thailand.  This is also issued to their family members traveling with them.

Tourist Visa

In Thailand, tourist or TR visas can be granted for sixty days or up to thirty days depending on the nationality of the applicant. All citizens of nineteen countries having an agreement with the Thailand immigration can obtain a visa upon arrival.  The fee for entry is about 1,000 Bath. The requirements for this visa are listed below:
  • Proof of sufficient funds for the duration of stay
  • Travel documents or passport valid for not less than six months
  • Recent photograph of the applicant with a size of 4 x 6 centimeters
  • Confirmation of an onward or return ticket

Types of Immigration Permits

Work Permit

Most foreigners who work in Thailand are subject to the Alien Employment Act H.E.2521. The term “work” is identified very broadly covering the mental and physical aspects of the job. Working without a work permit even for a day is an illegal offence.

Residence Permit

Foreigners with a residence permit can permanently live in Thailand without documents required for a work permit. They are not required to apply for an extension of a temporary stay in Thailand. The annual quota before granting the permanent residency in Thailand is a maximum of one hundred people per country. Residence permit holders have a number of privileges allowing them to:
  • Purchase a condominium or house without having to transfer cash from abroad.
  • Apply for naturalization in agreement with the law
  • Apply for an extended stay or permanent residence for a non Thai family member
  • Have a Thailand nationality granted to a child who is born in Thailand.

Re-Entry Permit

A re-entry permit allows foreigners to re-enter Thailand and use the remaining days stated on their visas. If such re-entry permits were not acquired, the visa will automatically be cancelled regardless whether the permit has yet to expire or otherwise. For you to make easy travel schedules, this re-entry permit can be obtained from Chiang Mai, Phuket, Don Muang Bangkok, Sukhothai International Airport or other designated immigration checkpoints in Thailand.

Change of Visa

The Thailand government gives foreigners, particularly those who have not applied for non-immigration visas before arriving in Thailand, the ability to change their visa should they want to stay longer in Thailand. This process can be done in Thailand. A foreigner qualified for a change of visa should enter with a transit or tourist visa granted by a consulate abroad or the Thai embassy. Foreigners should apply for a change of visa not less than 30 days before their current visa expires.

There is a post in Thailand Expat Forum last June 21, 2009:

Well there is a double entry tourist visa, takes a bit of getting, but that's 6 months' worth. It is much easier to get in from your home country than from border countries to Thailand.

With on arrival road border stamps only being valid 15 days, it's very difficult to stay using that method exclusively, which is the intention of the authorities (to make it difficult for those not on some form or other of long-stay visa). It can be done though. As of quite recently the rules changed - now a land border stamp is only valid for 15 days. That means that you have to do a border run every two weeks, to a maximum of 4 permitted. The next border run has to be by air. This gives a stamp valid for 30 days, and resets your land border count (you can do another 4, 1 every 15 days, until you have to do an air border run again. etc.)

Otherwise certain long stay 1 year non-immigrant visas can involve depositing a lot of money with a Thai bank in Thailand several months before arrival - but you can only get a bank account when you've arrived in Thailand and when you've got a permanent Thai address. Catch 22. For example, for a retirement or marriage Non-immigrant 'O', one method involves a long term accommodation contract, getting bank account and depositing 800,000 Baht or 400,000 if married to a Thai national, without letting the amount drop below that figure (1), then going to a visa friendly country (ie not Phnom Penh etc) to try to get the non-immigrant visa. But... for this visa you need to provide a reason and supporting paperwork for the long stay. Various non-immigrant options include work, study, family, retirement, becoming a monk and getting medical treatment. The list is available on this government site of all the options.

Work visas are very difficult to get, very difficult indeed. I would forget any thought about trying to get one based on your Internet business, there are many hurdles - money, requirement to employ Thais, you name it.

(1) a combination of a lower deposited sum and proof of regular income/pension is possible

Anyway check out the government site, the above are guidelines only, rules change, and I'm no expert. I have found getting the non-immigrant O visas pretty easy in Europe, for family reasons - wasn't asked for proof of marriage or anything first time around, managed to get a multi-entry year visa, with proof of sum deposited in bank and long-term property lease, and little else. I had gone over on a 3-month tourist visa to start with.