If you've only got about 5 hours between flights, 4 hours at the dayrooms would be perfect time-wise. If it's and international-to-international connection, exiting the airport and re-entering could cost you an hour each way during peak times. Plus transportation to/from the airport and you'll have less than 2 hours of sleep, vs. 4 hours at the day rooms. Add onto that perhaps paying the 700 THB airport tax per passenger, if there's two of you, that's 1,400 THB. Even for a cheap hotel room you'll likely pay at least 2400 THB. If you're someone who needs to get a visa-on-arrival, then the time/money (assuming there's a fee for the visa) goes up even more. So in such cases the dayrooms do make sens for those who need some sleep during a short connection.