If I get an O-A visa in my home country, I know that I will have to go and do a 90 day check-in. When I do the check-in will immigration check if I have a bank account and if I have 800K in that account?
TLDR : Answer Summary
The 90-day check-in for an O-A visa in Thailand does not require you to show proof of having 800,000 baht in your bank account. The 800k requirement applies to obtaining an extension once your original visa expires, not during the check-in.