Yes, foreigners are allowed to work in Thailand if you have a valid visa, a work permit and is employed with an occupation that does not violate the Alien Employment Act.
If you are a foreigner and you intend to work in Thailand, you are subject to the Alien Employment Act, which requires you to have a work permit to be issued by the Department of Employment, Ministry of Labor, or unless it falls within an exception of the said Act.
The term “work” in Thai law is defined very broadly, covering both physical and mental activities, whether or not for wages or other form of compensation. Even volunteer or charity work requires a work permit in Thailand.
According to Thai law, foreigners can work in the country but factors such as the national security, as well as the need of alien labor for the development of the country is being considered. Thai nationals are still to be given priority.
Under the Alien Employment Act, the following occupations are closed to foreigners and is reserved for Thai nationals only:
According to Thai Immigration, here are the major requirements:
Australia, Austria, Bahrain, Belgium, Brazil, Brunei, Canada, Denmark, Finland, France, Germany, Greece, Hong Kong, Iceland, Indonesia, Ireland, Israel, Italy, Japan, Republic of Korea, Kuwait, Luxembourg, Laos, Macao, Malaysia, Monaco, Mongolia, Netherlands, New Zealand, Norway, Oman, Peru, Philippines, Portugal, Qatar, Russia, Singapore, South Africa, Spain, Sweden, Switzerland, Turkey, United Arab Emirates, United Kingdom of Great Britain and Northern Ireland, United States of America, and Vietnam.
If extending beyond 30 days, all foreigners must have a valid visa which can be obtained from a Royal Thai Embassy or Consulate prior to entry into Thailand. The exceptions are nationals of Argentina, Brazil, Chile, the Republic of Korea, and Peru who are currently allowed to stay up to 90 days after obtaining an entry stamp at the Immigration checkpoint of entry.
You must check with the Royal Thai Embassy or Consulate before you travel, as the lists of countries change periodically because the Immigration Bureau adds and removes countries as circumstances dictate. Aliens from all other countries who do not have agreements with Thailand must obtain visas before coming to Thailand.
Due to the revision of some immigration laws, Thailand has become a prime spot for retirees from Japan. This is because the immigration laws and other obstacles to foreign retirees moving to and living in Thailand have been removed. While subject to a yearly extension, foreigners over age 50 who wish to retire to the Kingdom are now free to do so. As a result, Thai retirement services industry is growing owing to these developments. Hospitals, healthcare, and resorts for the elderly in Thailand have been targeted by Japanese investors. The prolonged recession in Japan has prompted investors to move into the region, many eyeing small and middle‐sized hotels in scenic locations.