I am not sure if some one has asked this question on this forum before, but I am very much interested to know what are the laws and requirements to register an Interpretation/Translation agency as a legal company with Thai partners in Thailand? and what are the certification requirements for foreigners to work as interpreters/translators in major languages to work with this company? Any recommendation of a good law firm who have any experience in this particular field will be greatly appreciated.

There is no special licensing required for translation or interpreting in Thailand either for businesses or individuals. You would just need a normal company registration with Thais as majority shareholders and have a stamp made up saying "Certified translation" with company details. Often a further stamp is required from the Ministry of Foreign Affairs certifying a translation to be accurate (and legalising the signature of a foreign vice-consul, if applicable).

From my experience of getting Thai documents translated into English by translation agencies, most of the translators have little knowledge of English and probably just run the stuff through Google translate. The certifiers at the MFA are not much better and are happy to approve most of this incomprehensible garbage but will quibble over irrelevant technical details like how to transliterate the name of a Thai into Roman letters. I shudder to think what the results might be like for translating Thai into languages other than English.

It is not for nothing that Thailand is ranked only just above Kazakhstan for adult skills in English. Good luck in your new venture.