A TM30 is a document providing information on where you are staying whilst in Thailand and is sometimes required for doing things such as extending your visa, possibly applying for a Thai driver's license also (not sure) etc.. but it is not something you'd need if you are departing Thailand. Safe Travels ✌️
By living in Korea, do you mean your a resident there and can provide proof of residency documents? If you're not then you'll have issues applying through that website.
Even if that statistic were true which I doubt it is, he probably just made it up out of thin air, all it would mean is that the only people suspicious enough to hire a private investigator turn out to be the ones that are being scammed, which is what you'd expect lol
Would like an empty SIM card. I know some third party places that sell them for like ฿40 in the city, just wondering if anyone knows if you can get one at the airport.