To start with, you need FOUR days to see correctly the temples, including Bantei Srey + the River of a 1000 linga. Tonle Sap is a huge lake so a boat trip on or through is like one on a sea, boring ! Besides I do not see the purpose of going to Battambang if you do not stay at least one night there. My recommandation,: Spend one day exploring the SHORE of the Tonle Sap, with the amazing villages of Kampong Phluk and Kampong Klean (do ot go to Chong Khneas, too many tourists).
SO one day SR (visit the Angkor Museum) + 4 days tempels + one day villages = 5 days