Teppitak

Carrying a U.S. passport, I had no problem getting into thailand with on-arrival visa; my passport was valid for another 2months. I made many phone calls when I discovered this prior to my last trip. The immigration official even went on to tell me that I can have my passport validfor 15 days and they will allow me to enter the country with on-arrival visa for 15 days. I assume you'd need to have the outbound ticket to show that you'd be leaving at so and so date.

As for all other visas that you must get from the consulates, this 6 months rule most likely would apply. I think it as to do with the fact that thye grant tourist visas and give you up to six months to enter the country.

So to sum up.

On-arrival 30 days tourist visa (U.S. passport)- no 6 months requirement.

All other visa - 6 months requirement

I went to Thailand with less than 6 months left on my U.S. passport. I was worried at first but the officials at immigration services assured me that for the "30 days on arrival" visa from the listed countries (I assume USA, UK, etc) only has to be valid to the day you leave. (i.e. if you have 15 days left, they will give you a visa for 15 days and you'll probably have to show your return ticket.)

After talking to him and asking similar question repeatedly, I was relieved and decided to not try to extend my passport with the 15 days I have.

Please remember that U.S. is one of the countries which tourists entering Thailand receive on arrival 30 days visa. If your country isn't listed, you should get your visa ahead of time OR some people can apply for visa upon arrival - but in this case, you will need to have 6 months validation. I've been told by the officials there that they have refused Chinese citizen the visa because their passport expiration is too soon. i think the cost for the application is 1000BTH (~25USD) plus photo cost (2-3USD).

These are my personal experiences.