What are the costs and processes for obtaining a business visa in Thailand for myself and my family?

They are run by a British lawyer with in-house Thai lawyers and have been representing the interests of expats since 2006 they can assist with your needs and give you clear advice. I hope this assists 

If you already have your own company in Thailand, and there are active. You can asked Visa Non B from your country and the. your family must be have visa follow you. , now your information are made little confused, I am not sure that now you are in Thailand or still not yet. Many details of this can change or flexible according to details or actual work. For more information you can IB to me.

I've never used a lawyer nor a visa company.

When you set up a company, you'll need a certified accountant. Ask in your surroundings for a good reference. He/she will provide you with all required documents and if needed they can accompany you at immigration or they can send it to your home country where you also can apply for the non-B.

This is how I did it and I used to pay just the monthly 1.000 thb fee for the ongoing accountancy. 2 or 3.000 thb for preparing the Immigration file. I paid 12.000 for setting up the Company Limited and the creation of the DBD COMPANY STATUTES. (That's seperate from the cost for the visa itself ofcourse) This is/was however a few years ago in Chiang Mai but I'm guessing if you see rates more than double of that now, you're getting ripped off. You DON'T need a lawyer for anything else than litigation. As a matter in fact, they probably outsource this kind of work to an accountant themselves and charge you an exorbitant fee for it.

Non Immigrant visas are 2000bt and extentions of stay are 1900bt.