I don't believe Australia embassy certifies income. So that leaves out the 65k method. Funds in a non-thai account won't qualify for a 1yr extension of a non-o visa. You can get a non-oa visa showing foreign funds but it also requires specific Thai health insurance and criminal background check. A lot easier to simply put the money in a Thai bank account and forget about it.
You will need to take the bike to the dlt in your provincial capital. You will need bill of sale, signed copies of your and sellers ID, residence certificate from immigration and the green book. Be sure the bill of sale is witnessed by 2 people not part of the transaction.
You might find it easier (if you have the means) to increase your 400k to 800k and apply for the non-o and extension based on retirement. Much less paperwork and you're not tied to your marriage for your extensions (or if you're wife should pass). Less paperwork and easier process.
Depending on how long you plan to stay in Thailand, you probably don't need a visa or any extensions. Each visa exempt entry currently gives you 60 days which can be extended by 30 more if you need it.