If you don’t have a Thai bank account you should apply at home for the non-o visa which will help in opening a bank account and transferring the 800k which needs to be seasoned for two months before your 1 year extension and keep it there for 3 months after
Only opening for long stay visas best to get a non-o before you come then get the 800k in it quickly unfortunately in Pattaya you need the 800 k seasoned for two months before you apply for the Non-o making it impossible forcing you to use an agent