Cebu Pacific Airlines, Singapore
From Bangkok going to Siem Reap - there's an airline called CEBU PACIFIC (www.cebupacificair.com) but the route is BKK - (via Philippines)- Siem Reap - but the price is cheaper and they do always gives promo on a specific travel period or until seats last. You may try it then. c",)
I think Cebu Pacific flies out of Budget and it is possible that you may not be able to check your luggage through. in which case, clear immigrationa and customs ( a breeze ), take a taxi just outside ( a breeze), go to hotels81 in jhoo chiat lane, the red light district of singapore, a more interesting part of singapore, people wise, lots of places to eat and drink and also very reasonably priced hotels and not too far from changi airport and then return to changi airport. the budget terminal is not that good but the main terminal 1 is one of the best airports you would want to be stranded in. In fact, I find Changi Airport to be far more interesting, from a social and cultural point of view than the tractof land that is singapore..