Will a lost passport cause issues with my overstay in Thailand?

Go to your embassy and get a emergency travel document and leave and you will pay the overstay fine when you leave if caught on overstay they will lock you up until you produce a ticket home

In some countries at least. It is possible to get a paper thin emergency passport at the embassy

Valid 12 months!

I did the exact same thing last year and I got fined 500 baht for each day of overstay 💀

For future ref: I screen shot my passport and keep that copy on my phone. My passport I keep locked in a safe and never take it out with me, unless absolutely ness

Lost a passport once in Thailand. I filed a police report and then went to my embassy to apply for an emergency travel doc, which provided a single journey out of Thailand and back to country of residence. Perhaps your embassy can issue the same and you can avoid the lengthy overstay. Just an option.

But i would add 'losing my passport on the day my visa expires' is not advantagous in anyway. (Or losing it all). You need to report to the police today, and be really nice and apologetic, as dealing with police as an overstayer is never a good idea. I suspect they wont be to pleased if you applying for a new passport comes up in conversation, rather than needing the report to get an emergency travel doc.

You won't be able to re-enter until you have a New passport.

𝗪𝗶𝗹𝗹 𝗜 𝗵𝗮𝘃𝗲 𝗮𝗻𝘆 𝗶𝘀𝘀𝘂𝗲𝘀 𝘄𝗶𝘁𝗵 𝗮𝗻 𝗼𝘃𝗲𝗿𝘀𝘁𝗮𝘆 𝗱𝘂𝗲 𝘁𝗼 𝗮 𝗹𝗼𝘀𝘁 𝗽𝗮𝘀𝘀𝗽𝗼𝗿𝘁.

Nope show up with the police report and the new passport when you stamp out, they'll look up your previous entry stamp, fine you 500 baht a day overstay fine and stamp you out of the country.

𝗪𝗶𝗹𝗹 𝗜 𝗵𝗮𝘃𝗲 𝗮𝗻𝘆 𝗶𝘀𝘀𝘂𝗲𝘀 𝗿𝗲 𝗲𝗻𝘁𝗲𝗿𝗶𝗻𝗴 𝗶𝗳 𝗜 𝗵𝗮𝘃𝗲 𝘁𝗵𝗲 𝗽𝗼𝗹𝗶𝗰𝗲 𝗿𝗲𝗽𝗼𝗿𝘁 𝗲𝘁𝗰 𝘁𝗼 𝘀𝗵𝗼𝘄 𝗜 𝗹𝗼𝘀𝘁 𝗺𝘆 𝗽𝗮𝘀𝘀𝗽𝗼𝗿𝘁.

In and of itself a couple week overstay shouldn't affect you getting back in but keep in mind the fact you lost the passport cuts no ice with them as far as whether you'll have issues entering or not. That is totally going to depend on your previous entry/stay history to thailand.