Don't listen to any of the naysayers and trolls on here. To get married legally is easy. Just go to the amphur with your gf/wife and 2 witnesses. You can sign all the documents at the amphur in Thai, and it only costs 80 thb. I was previously married to a Thai divorced and remarried a few months later (we had been separated for 8 yes).
but YOU are in Thailand and therefore YOU are working in Thailand. Where your clients are isn't the issue but where YOU are. Therefore you need a work permit although I read somewhere that there are new laws and visa pertaining to remote workers that circumvent this but I believe you need to provide vproof of income from overseas etc.
Why only $50k, this is insurance in case you get CoVid, the fact that you stay 1 or 14 nights doesn't change the cost of chances of your getting CoVid so why would the insurance be less??
I've been married to a Thai 10 yes and my first wife of 5 years was Thai and I've lived there since 2004, so I do understand but prenup isn't the answer.