All work in and from Thailand requires a work permit issued by the Department of Labor. There is a new 10 year LTR visa that is administered by the Board of Investment, but applies to those who either work remotely for a “substantial company” (publicly traded or $50M in revenue/annum), or who are highly skilled as defined by the BOI regulations. If you might qualify it’s worth checking out on the BOI/LTR website. Otherwise you may consider working for a Thai company and obtain a work permit and Non-B visa through that entity. I appreciate that you’ll get advice that enforcement for those working remotely is difficult and hit or miss, the consequences can be troubling if you intend to make Thailand your long term home. Best of luck to you, and here’s an article on the LTR program:
*******************************************************************