a official document stating the the LLC exist and is register in the country. When you have create your LLC, you probably have a official document proving the registry of it ? ( and showing that you are director/administrator ? )
Basically, every outside thailand income you bring to thailand is taxed between 0% to 30%, but you can short it with tax you pay outside thailand for that income.
Basically if you have a lot of saving before coming to thailand, you will pay 0% for long time ( depending of the amount of your saving ). Plus, with tax thai resident, you should be able to lower any tax in the country of your income.
The money have to be in your perso nnal account and not business account. But they may ask for invoice/payment of your business to see that you have activity/income ... to many people cheat ...
Participant(e) anonyme you show the way you get it or buy it. You still will have to pay tax capital gain. ( if the value of your crypto now is more than when you buy/get it )