Will I be admitted to Thailand on a 30-day visa exempt entry if my flight is 56 days from entry and I plan to apply for an extension?

As a US citizen entering Thailand on a 30-day visa exempt entry, it's likely that you will be admitted even if your flight leaves 56 days from the date of entry, especially since you plan to apply for a 30-day extension. Many travelers have reported not being questioned about their return flight if they maintain a polite demeanor and do not mention the extended stay plans upon arrival.