Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Singapore to Redmond as you normally would.
Bend/Redmond (RDM), located 2.8 km from the city centre, is the airport you fly into when you book flights from Singapore to Redmond.
This is defined as Singapore Changi Airport (SIN) and Bend/Redmond Airport (RDM). Codes like Bend/Redmond Airport are often used to just call airports uniquely.