Hi, i do not consider myself a specialist on visa issues, but some years ago there was a similar (and even worse) problem for a guest at the same resort. IN SAMUI.
Czech women, travelling together and not the first time. Staying three months as usual and not familiar with any details as the tourist is usually taken care off.
One of them just found out, that her visa wasn't used and she only got the 30 days AND was already on a relevant overstay.
She was nervously telling this to the massage women as she was scared to tell the resort owner (an old man we knew for more than a decade and even called him papa, but the czech woman was afraid, he might be angry.). She asked him and he was urgently telling her to fix it. Now she was more nervous about what to do and the massage women, who also knew us some years, suggested to talk to me. I told her the simple truths, that it is serious, but can be fixed. That she needs to do it as soon as possible, which means today (as it was a normal working day, immigration open). I told her, that she could be arrested and deported in case she gets controlled on the way to nathon, but hardly will happen, and she should not worry, but just go there.
Now i gave the advice, i think, is the most relevant:
Get dressed properly. Long sleeve, trousers or long skirt. Clean. Wear a bra. No slippers but closed shoes and maybe even socks. It does not matter if you sweat.
When you adress the IO, do not say "You made amistake." Say: "I have a problem, can you please help me." (For my experience over more then three decades, Thais will help you, if asked nicely.)
She went nervously. Came back some time in the afternoon, studying the new stamps with her fellow girls and the massage women, cause they were not sure about the meaning calling me again for help, if this would be OK.
I looked at it and they now stamped the tourist visa (still stickers that time) USED changed the dates and signed extra stamp. Still no expert, to me it looked absolutely fine. I asked her, if the officers were angry, made problems, asked for money or anything uncomfortable happened. She answered: Not at all.
for my ten cents: Go there - you are not even on overstay. Mind your appearance. Mind your words. Show trust. And you'll be fine.
(The TM30: when your AirBnb asked for your ID, they might have done it. If they didn't and the IO critizises, tell them your true stay, cause it is the duty of the AirBnb, and if they haven't taken care of you, their trouble should not be yours.)
regards