translation agency and work permit

Some of my friends, recently visited Thailand for short term work as interpreter with official delegation,

he frequently comes to here 4-6 times a year for this kind of jobs, to stay about 1 week or less each time,

he asked me about staying and working in Thailand,

I never heard about such type of companies before,,

how to register a company or just tranlation / interpretation as commercial service?

How about paying tax? how to apply for workpermit for this?

also he said this is not a regular daily job, but he often receive some projects for translate documents, websites, interpreter in official events, 

and does this required to employ thai workers? as no any need to any, he operates his business from his website,

can use a rented condo to register this translation / interpret service? 

Thai language is not in his business of translation, to make this clear. 

Any ideas about this? and how much the cost to register,, etc..

Thanks