Are you booked through Thomson? The hotel still shows on their website and I doubt very much a huge company like TUI would continue to sell package holidays to a hotel if there was anything majorly wrong with it or it had closed. Bare in mind that it's been the 'off' season in Khao Lak since the last (English language) review was posted on TA so that might account for the lack of activity. We're booked at the Sensimar through Thomson (also in November) and even though it's seemingly a much bigger resort in a busier location, reviews have also been slow going, I check almost daily for new ones. Have you tried contacting the hotel via email to confirm your booking and check everything's okay?