Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Surabaya to Aruba as you normally would.
For a flight from Surabaya to Aruba, you will be flying from Juanda. Surabaya Juanda (SUB) is just 15.0 km from the centre of the city.
This is defined as Surabaya Juanda Airport (SUB) and Oranjestad Reina Beatrix Airport (AUA). Codes like Oranjestad Reina Beatrix Airport are often used to just call airports uniquely.