For a start you have to be over fifty years old. If you are, then if you can provide a bank statement showing at least 200,000 THB, equivalent in your own country bank account, then apply for a 3 month non-immigrant 'O' visa in your own country, then when in Thailand you can apply for a bank account & then do a transfer from your own countries bank account of the equivalent of ,800,000 THB to your new Thai account then you can apply for the visa retirement extension. When your in Thailand, go into an immigration office and ask for the requirement process you need to go through to get this extension.
Duurgh! If you brought it into Thailand as foreign currency, why would a cash deposit that obviously would be exchanged at the bank to want to deposit at, along with the exchange paperwork, not be accepted? Also, they said they brought 800,000 THB equivalent in a foreign currency. Then you say that the 800,000 is required to come from overseas which is not true of a cash deposit. If it's foreign currency why would it not of come from outside Thailand?
who'd want to buy a house when the land it is on is owned by someone else? Only a fool in countries that don't have water tight protection for the property owner.
You can legally own 49% of shares in a LTD., company and the assets (house) can be the asset of the company, including the land. Been there, seen it, done it.
Many many years ago I did visas both in Singapore & Penang. In both cases, as is usual with all Embassies/Consulates. Apply with correct paperwork and payment in the morning and get visa next day afternoon.
I opened an account with SCB in 1999 on a VOA. Unfortunately after I left Thailand and my funds in this account had been withdrawn by Thai, the bank closed the account. I still have my old passbook & debit card. When I go to Thailand later this year, depending on which visa I get from my home country, I'll go to an SCB branch and ask if I can open another account. Can but try.