Don't use autofill. It often doesn't work. While I have so far never dealt with the Thai e-visa system, I deal with the Cambodian and Vietnamese ones a lot.
On the Cambodian one I did recently (for a business e-visa) I allowed the system to do autofill, then I had to go back and manually fill in all the fields. In the end, they didn't have a copy of my passport in the system when I went to check my application later.
I added one, but this reset the processing time, in the sense that the system told me I now had to select an entry date 3 days later. I probably shouldn't have touched it.
Fortunately, just 5 hours later my visa was issued.
Now of course, the Thai e-visa system may be different, but the point of my story is to be very careful about how you fill out these forms and don't go back and make amendments after submission unless you're able to contact someone about it or the system actually allows you to. Some don't.
Precisely. It doesn't even register to them that you may be living in Thailand.
At mainland European airports on the other hand, especially when departing from Switzerland (regardless of whether its on THAI or Swiss) check-in staff don't check for onwards tickets or visas. They just issue you with a boarding pass.
Australia used to be like the UK, but is now less strict. America is quite strict, similar to the UK.
Don't worry about the guarantor in Laos. Just put someone in Thailand or back home. I know people in Laos, but they can't expect that to apply to your average foreigner just passing through town on a visa trip.
If so, they should have seen that, unless they didn't bother to check.
With an e-visa, one must always hand a printed copy over to the check-in agent (don't wait for them to ask, do it automatically without saying anything) because without that proof, they'll assume you're coming in on visa exempt and will ask for outbound flight proof.
Forget about the guarantor part of the application form. I don't think they care what you write. Put someone back home. Or a Thai person you know (such as a spouse) or close friend or something.