How spicy is it? Ive never used Thai chilis and Im cooking for someone who is a minimal spice person

I think this entire dish would likely be way too spicy hot for somebody you describe as a minimal spice person. Most Thai chiles clock in around 15 times hotter than a jalapeno, and in my experience minimal spice tolerant folks find those nearly unbearably hot. Even the gochugaru flakes will be about twice as hot as a jalapeno, so the chile oil is also likely to be a bit more than your friend will care for. If you want to take a stab at it anyway, I suggest cutting way back on the number of the Thai chiles, perhaps to just part of one. And I would definitely de-seed and de-rib those, before tasting to assess spice/heat level. I'd also consider using less of the gochugaru in the chili oil, and perhaps more oil to dilute that heat level. Though honestly, this recipe might not be the ideal choice for a person who doesn't enjoy spicy or hot food.