I recently messaged the JWM BKK for an upgrade prior to my stay. They replied it would be granted if one was available. Checking on-line 24 hours prior to arrival, it said I would be in a suite - so I printed out the page from marriott.com.

Arriving at the hotel, the agent said, "I see your request for a suite, but unfortunately we have none available. The Guest Relations Manager has assigned you a non-smoking king." I told her of the pre-arrival notice and showed her the print-out. Two minutes of typing and one phone call later, and I was in a suite with no further questions asked.