- For the online system, will the TM30 from my hotel/temporary apartment in the South cancel out my TM30 for my condo in Chiang Mai (making it not possible to do the 90-report online)? Or will doing the 90-day report with my Chiang Mai condo still work?
- Other than the 2000 baht fine, are there any other negative ramifications from doing the 90-day report, say 1-2 months late?
There is no 100% chance you'll make it in. However, having an expensive pre-paid ticket from Bangkok to Tokyo is decent proof, if you are ever questioned. Even print your hotel room in Tokyo. Was your Singapore to Tokyo tickets bought together (with a DMK-BKK airport transfer being part of that)? Something else you can show, if that's the case.
I've never done this before, so maybe someone can confirm, but do you have to stamp "into" Thailand (with a shuttle or something), if you simply have to transfer between airports?
7-day rejection stamp that Alistair explained is the best option. If you overstay, this might create issues for any future visits to Thailand, or when applying for a visa.