I am arriving into BKK at 11:25 PM and flying out at 7:00 the next morning to Siem Reap and Angkor. All the books say there are two transit hotels inside security. Has any FTer stayed there?

Also, I want to leave a bag at the airport and pick it up on my return to BKK. I know that there is a 24 hour luggage service at the airport. Does anyone know if this service operates inside security so I don't have to go through Thai Immigation? Thanx.