@Kevin *****
don't use an agent (other than maybe to open a bank account) it's easy.
Once your bank account is open, deposit 800,000 baht, ensuring it shows as an international transfer (if using Wise use the code to state you are buying property, this changed recently).
Go to immigration and ask for their requirements for a non o retirement.
Supply the information they request and pay the fee.
2 months later apply for a 1 year extention.
It will likely be the same documents plus some information from your bank.
Repeat the final (extention) once a year.
Good luck.