IF your visa exempt, and dont have a long history of trips this year, you should be Ok they want tourists not people living here on visa exempt. Be prepared to chat with the immigration officer.
How does an agent open a bank account? Do you know anyone whos really done that? Part of the process is to verify who you are, this involves the bank checking your non o visa, taking your picture, verifing your address, and whatever the local bank manager decides whats neccessary to prevent fraud, IF an agent could do this illegal you would face the account being closed later when you wanted to change something on the account when they check the bank account details.
Thai General Insurance Association (TGIA). Their website longstay.tgia.org provides an approved list of member insurance companies that offer health insurance plans compliant with the O-A visa health insurance requirements