This video by Chaninat & Leeds law firm discusses the registration and operation of foreign NGOs in Thailand and details how non-Thai NGOs may establish activities in Thailand.
The preferred operating form for an NGO operating in Thailand is normally a Thailand registered foundation.
There are many volunteering opportunities available in Bangkok: from social issues, to environmental issues, to health care issues, to minority rights, to human rights, however there are also a number of areas that foreign NGOs are not allowed to operate in Thailand.
Watch the video here: