To add a little detail to JohnSIN's post,.... Take the Phaya Thai Express train from the airport. 90 baht, maybe about 20 minutes. At Phaya Thai, walk to the BTS/Skytrain. The walk is entirely elevated and within the structure. At BTS/Skytrain, take a train headed towards Bearing. Get off at Asok station. Go down one level from the train platform. As you come down the stairs, you'll see a sign hanging from the ceiling at the bottom with exit numbers and where they go. One of the destinations is Sheraton Grande Sukhumvit, I think that it is exit 5. Then just follow the signs for the exit you want. The elevated walkway you take through the station goes right into the lobby of the Sheraton.