[ableChair]

The word is slang to begin with, so neither spelling is 'correct'. The military uses the term to turn the word 'laser' into a verb.

[Leroy S. Mort]

The word is slang to begin with, so neither spelling is 'correct'

Not to pick nits, but "lase" certainly is a word. It's in the dictionary.

lase
intr.v. lased, las·ing, las·es

To function as a laser; emit coherent radiation by the action of a laser.

[RightOnTheLeftCoast]

"The word is slang to begin with..."

Wrong. It's an acronym: light amplification by stimulated emission of radiation.