Do I need a visa to travel to Koh Samui from the U.S. if I plan to stay for 2 months?

no

So glad you are escaping America for the 1st time. There is an amazing world out there to discover.

Very easy Google transit visa requirements for country you are passing through. Most do not require a visa if you do not leave the air side of the airport.

All you need to know is at the American Thai Embassy site...

US passport gives you 30 days (visa exempt) on arrival. You can easily get a 30 day extension and experience the simple process to do this at the local immigration office (get up early that day!). You need proof of onward travel (or a return ticket) to board your flight to Thailand or they won't let you board. If you're staying 60 days, you can have a return flight prior to the 60 day period ending. It's highly unlikely that any airline wouldn't accept that return ticket as proof of travel out of Thailand. In the one in a million chance that you should have a problem at the ticket counter then you quickly book a $59-$69USD cheap flight to Vietnam or use the onward ticket website for $20. Have fun!

if ur travelling on a US passport, staying for only 2 months and returning back to the states

Apply in advance for a Tourist visa online ( valid for 3 months for a 60 day stay)

NO hassles at all

enjoy

You'll need a visa or proof of onward travel if you're staying in Thailand for more than 30 days.

If you go on visa exempt, 30 days without visa, and your return ticket is only after 60 days you may be having a problem at your check in or immigration. Take a visa for 60 days or get yourself a fake onward ticket on day 30.

If with US passports you should apply for 60-day tourist visa from Thai embassy, believe it will be done online. Once in Thailand you can apply for additional 30 day extension of stay for tourism. Need more than those 90 days and you can leave and re-enter Thailand on visa exemption which will allow 30 days stay, which can be extended by additional 30 days for reason of tourism at localThai immigration for 1,900 baht. All told that's an easy 150 day stay.

If you are travelling on a valid US passeport, you don't need a visa. When you arrive at the airport and pass immigration, you will receive a free stamp that will allow you to stay in Thailand for 30 days (make sure you have 1. at least 600 USD in cash 2. A accomodation booking for the first days 3. An exit air-ticket for date shorter than 30 days. If you want to stay more than 30 days, you go to immigration office in Thailand and buy an extension of stay of 30 more days, for 1'900 Baths (at 60 USD). The details are on Google...

"Travelling from" is not same as being US passport holder. Information may vary depending on what the facts are.

It literally states on the website.

No need. US passport doesn't require a visa here in Thailand. Lay over doesn't require a visa as well as long as you don't go out of the immigration ( depends on what country)

Why are people laughing at this post? Seems like reasonable questions from a rookie traveller. Be kind. We need an admin to jump in and help with this one.

Canada may require a transit visa depending on nationality. As I understand, your visa will be a sticker in your passport, taking up the entire page. This visa may have your dates of travel printed on it. There is no stamp as far as I know. I don't know about extensions with American tourist visas, because visas are supposed to be issued by your home country usa embassy. I was led to believe that if you wanted to extend, you had to travel back to (if you're thai) us embassy bangkok and then return to USA again.

Needs a clear question. What countries are you stopping in. Only two countries i know that need visa for transiting are India and the States

Single entry tourist visa will give you 60 days plus 30 days extension in country.

Multiple entry tourist visa can give you up to 9 months if you time it right.