Not that difficult to do yourself and documentation is in English; immigration officers speak English. Your local Thai embassy site will detail the process, easiest way , apply for a 90 day Non O and then extend for a year in Thailand.
It is all done online and you can be asked for an interview. London is fairly quick with approval often within 5 business days and going by postings rarely asks for interviews. You need to provide a contract of employment, detail how you work online for non Thai firm/clients.
No life insurance cert needed. Expect around 10 business days for approval. Chances of getting are the visa are very high if you submit the docs and financials requested.