Rays are easy to identify, for the most part. Their pectoral fins have expanded to become "wings" that propell the ray through the water. Like sharks, rays don't have bones but have a skeletal structure made of cartilage. Many rays do have a stinger in their tails, which should be avoided.
Crown-of-thorns starfishh
Scientific name: Acanthaster planci
I haven't pinned down exactly which pipefish this is, but I believe I have the right family. Best guess is it's a Shultz's.
Manta Ray
Scientific name: Manta birostris
Mantas are the largest of the rays, and among the largest of all fishes. They also have the largest brain to body ratio of all the sharks and rays, which might explain why they're relatively curious about divers. Rather than objecting to our presence, they often come to investigate divers. In Hawaii, where the photo was taken, they even seemed to enjoy putting on a show for the tourists.
Southern Stingray
Scientific name: Hypanus americanus
This juvenile was snapped at Gibbs Cay near Grand Turk. It's a popular stop for tourists and divers where the rays are used to being fed by the guides. The rays will rub up against your legs like hungry cats. Like cats, their skin is actually quite velvety.
Blue Spotted Ray
Also called: Bluespotted ribbontail ray, blue dot ray
Scientific name: Taeniura lymma
The blue-spotted ray seems to be the most common ray that you're likely to see around Southeast Asia. I've seen them in almost every area. Note that this is a stingray, so you want to keep your distance from the tail.
Torpedo Ray
Also called: Electric Ray
Scientific name: Torpedo marmorata
Torpedos are a large group of rays, all of which are capable of delivering an electric shock.
Yellow Ray
Scientific name: Urobatis jamaicensis