Siem Reap is about 187 km from the ocean.
If you're driving to a town near the beach or coastline, you could try Trat.
How far is Nashville from the ocean
How far is Traverse City from the ocean
How far is Knoxville from the ocean
How far is Charleston from the ocean
How far is Spokane from the ocean
How far is Kihei from the ocean
How far is San Pedro, CA from the ocean
How far is Boise from the ocean
How far is Cincinnati from the ocean
How far is Hong Kong from the ocean