It doesn't matter - it's a case of self-declaration and regardless of what visa you hold, you can't select Thailand as your country of residency using this form.
2. Yes - but Vietnam generally requires a tour. Laos, Cambodia, Malaysia and Singapore are the destinations for which you have free reign on a Thai registered bike or car.
I can't imagine they wouldn't do an eyesight test in Krabi though as that is literally done everywhere and I've done it in multiple locations around the country over the years. All 4 tests take a combined 5 minutes or less.