'I will be travelling to Thailand in October with an American passport with only 4 months before expiration . Will I have any problems?

Yes, your passport needs to be valid for 6 months when you arrive. I would renew my passport before you go. You should have time to renew it and may be able to do it by mail. The State Department website provides details of how: http://travel.state.gov/content/passports/english/... If processing times have you worried that you will receive it in time, you can also hire passport service companies like Rush Passport: http://click.linksynergy.com/fs-bin/click?id=u5gSY... who (for a fee) can expedite the processing time for you.

Yes. Renew it now, avoid tons of problems.

You'd better be sure you're back by that time, otherwise no problem.

Yes, renew it now.