@Alan ****
you simply come in on a visa exempt entry that is for 60 days. During your time here you want to base out of Bangkok to visit other countries, and that is no problem. You are being an actual tourist. Lots of people do this as you can go anywhere in South East Asia from Bangkok in just a few hours. There is no limit on how many times you can do this. I personally know two people that have been doing exactly what you want to do for over two years now, with no problem at all leaving, and coming back to Bangkok. You are not trying to live in Thailand long term as a tourist, and are actually being a tourist visiting other countries. All you need is your passport, and your money, and suitcase. Immigration will be no problem at all for the plan you have.