Should I apply for a Non-Immigrant Type “O” Retirement visa or a visa exempt with extension for my first trip to Thailand?

Getting a Non-O sorted before you come on your first trip will enable you to get your bank account sorted early so you don't have to rush it at the start of your retirement.

And getting a Non-O on your first visit lets you avoid going to Immigration during this visit. 🙂

Just travel around, find your pace, enjoy your life, no extensions needed.

And then in 6 months come back armed with a Thai bank account seasoned with the required amount of money for the upcoming yearly extensions, without having to stress to arrange it all out on arrival.

Getting a non O is easy. If you plan to open a bank account on the first trip you need the non O, not visa exempt or tourist visa.

You can not open a bank account on anything other than a long term visa so best get it in your own Country to save a wasted trip.

Sounds like you're doing an exploratory trip first. Just go with exempt. When you run and have plans for your move, get a non-o through the evisa system. You can then rent a place, open bank account, etc.

You should apply for the non I'm on visa in your home country, the you will be able to open a bank account. Without the correct visa a bank account is not possible nowadays