Not necessarily a derogatory term unless an Asian person takes it as so. Most Asians who do smoke pot have distinguished a fine line between the derogatory term (Chink) and this term. And I've met some cool Asians that will allow you to say the latter without shooting an AK-47 at your head.
This is just a term to describe the squinting eyes that one gets when taking the drug, Cannabis.
A descriptive term used to reference a person under the influence of marijuana. One of the symptoms of this popular drug is red squinted eyes. The squinting of the eyes creates slanted eye look. So chink a negative slang word used when referencing someone of asian decent is descriptive of the appearance of the eyes. An additional symptom is lethargy, slow moving pace when high on marijuana, or flu like behavior.