@Lauren ********
Yes I thought that may be the case but I thought it was a rule in Thailand that you cant be without your passport. A rule made by the Thai government. I just did mine for a replacement, the agency that deals with UK passports voided the old passport when the new one was sent back. I thought I had to send my old one but no, I was advised I have to keep it. Just had to photocopy every page etc. Good luck.