What type of visa should I get for a 2-month stay in Thailand and how do I extend it?

Just get tourist visa on entry 30 days then get extension. If you going to other countries you can get another visa when you come back to thai. Its easy your going on holiday. People love to make things complicated you dont need cash at the airport just plastic. They have seen bank cards in thailand. Its a whole lot harder to get into the states than it is thsiland

If you want to travel in and out of Thailand as you visit other countries I'd suggest a multi entry Tourist Visa. Valid for 60 days but unlike the single entry you can come back to the Kingdom should you desire .

You mentioned that you're planning to travel to other countries in the region. You should know that your single entry 60 day tourist visa AKA SETV (if you decide to get one at the Thai Consulate in the states) is only valid for ONE entry to Thailand. So, you enter, you get 60 day stamp in your passport and your visa is stamped "USED". If you then leave Thailand, you lose whatever days remain on that entry. So, if you plan on leaving Thailand within 30 days of arrival, then the SETV is not the visa for you.

If you are planning on travelling around to other countries (good idea...explore while you're here!) then just come and enter on the 30 day exempt entry. Then, anytime you travel to another country and come back to Thailand you get another 30 day exempt entry. Only caveat is that you are only permitted 2 visa exempt land entries per year (unlimited if flying).

One item to note though is that some airlines might not let you travel to Thailand without a visa in your passport. But, assuming you have a return flight, you can explain to them that you're entering visa exempt and, might work. All that being said, if you do plan on staying in Thailand for more than 30 days, definitely get a 60 day SETV as it is a cheaper and easier option with less headaches.

assuming that you have a USA passport, there will not be any problem getting the 30 day extension. You don’t need a visa to enter.

Best option is to get a Single Entry Tourist Visa, which gives you 60 days permitted to stay on Entry in Thailand. You can buy one at the nearest Thai Consulate or Thai Embassy.