We had the same situation for not having our US marriage certificate to certified from secretary of state, US department and Thai embassy. We sent our original marriage certificate back to US and did certified. Also we use the the US to fill the form and mail our marriage to Secretary of state and US department for us. It cost $580 (exclude certify from Thai embassy in US) and took about 2-3 weeks for documents to get done and mail back to us in Thailand. Also I took my husband to get non o spouse in Vietnam but since you already have non o from US I believe you only have to mail and certify your marriage certificate in US and wait in Thailand until you receive the document and if it doesn't get to Thailand during your 90 days for non o to stay in Thailand , you have to go apply non o outside Thailand again and come back. After you receive all documents from US then you have to go to department of consular affairs in Chaengwattana to translate in Thai and certify all documents from US again before you start open the Thai bank account. I deal with all this process in April and just done it 2 days ago. 🙂