You can get the 1 year multi entry visa if you qualify, which usually means you have to be married to a Thai girl. You use to be able to get one if you had a child that had Thai citizenship, but there is a recent change that no longer allows that. Depending on which consulate you use, you may or may not be able to still qualify that way. Just getting a 1 year visa because you want to live there will not be possible.
You could get a tourist visa, they are either single or double entry only.
You are probably thinking about a visa-free entry, which is allowed for US passport holders. You can get 30 days if you enter at an airport or 15 days if by land. Unless you want to get a bank account or drivers license, that will usually be sufficient.