You do not need a lot of paper work or documents to work in Thailand if you have the legitimate visa and authentic work permit. The work permit is required to be kept in office where you work so that it is available for the immigration officer for inspection always.
To avail a work permit for Thailand you should either have immigrant visa or a non immigrant B visa. The non immigrant B visa is requested by a couple of embassies to give you work permit or a module WP2 for a work permit application which will be a condition for the issuance of an immigrant visa which is not a B.
There are no hard and fast rules of applying for a work permit in Thailand; it can be pertain for both visa and non immigrant visa. Only non Thailand residents with non immigrant OA visa (retirement) will not be permitted a work permit for Thailand.
You are given a work permit only on the condition that your course of work will be legitimate and not contradict with any Thai law of work and labor. It should be in accordance with the traits and customs of Thailand work styles. The work permit will give permission to practice trade only which is stated in the work booklet and the trade is allowed only in trade places and locations permitted by the Thai law.
Foreigners who are interested to work in Thailand are obliged to submit certain documents to apply for the Thai work permit. These documents include a request for work permit singed by the applicant, copy of departure card, map of the company you wish to work in with the signatures of its mangers/ owner, copy of applicants passport, medical certificates, three colored photographs, copies of training certificates or diploma degrees, marriage certificate is case of spouse being a Thai, and tax forms.