We went to the Sala Samui last year and stayed in a pool villa and the pool was actually 5m x 3m....could manage about 3 arms of front crawl but it was enough just to cool off really. The best thing about it was the 10ft wall surrounding the villa so we had complete privacy.

The pools in the Renaissance photo's look about the same size but perhaps they have been stretched for effect? maybe the best thing to do is contact the hotel and ask to be put into a secluded spot to assure privacy and ask the size of the pool at the same time......