Place stock in a pot and set over high heat.
Add the turmeric, saffron threads (if using), garlic, fish sauce, lemon juice, cumin, and chili. Stir well and bring to a boil.
Add the rice, shredded coconut, plus coconut milk. Stir continuously (to keep rice from sticking to the bottom) while you bring liquid back to a gentle boil.
When liquid is gently bubbling, reduce heat to low (just above minimum) and stop stirring. Cover pot tightly with a lid and cook about 15 minutes, or until liquid has been absorbed (use a fork to pull rice back so you can see to the bottom of the pot).
Turn off heat, but leave the pot on the burner (covered) to steam for another 5-10 minutes, or until you're ready to eat. Rice will stay hot in this way for an hour or more.
Before serving, fluff rice with a fork and taste-test for salt.
Garnish with the green onion, & serve.