If you arrive visa exempt they are currently stamping for 45 days, so after ASQ you have 29 days. Just visit your local immigration office and explain you want to convert to non O for retirement purposes.
Forgot to say all packages coming into Thailand depending on what it is is subject to VAT tax 7% import tax again you need to look it up depends on what is in the box up to 40% lol cars no no it’s 300% and maybe even a permit and license and Believe me they will open the package to see what they can make money off on ( corruption) but when you live here and order something to ship here again ( order from a store) it’s fairly easy and no problem that’s why I won’t have my sons ship me anything again last time a bunch of goodies and lithium batteries and tv converter holly crap I got fined on the batteries and need license and permits for the damn batteries and converter Jesus Christ!!!!!
Flight wise don’t matter save money go cheap. Any kind of money works $800,000 baht for retirement visa, $400,000 if married to a Thai. Money in the bank yes need to show proof of funds. Entering Thai there will be a waiting list and 2 weeks quarantine and crap load of forms being Wuhan free lol. As for moving depends how much stuff you have I shipped a 20 foot packed shipping container with ins. 2 years ago from Portland Oregon USA for around $2,500 on 8 weeks time to deliver but if you want faster it will cost more