I like my Thai food (and any other spicy food) five stars hot, but it really depends on the restaurant. My favorite Thai restaurant makes my four stars crazy hot, so I will never ask for five stars because my tongue and stomach will go haywire; at other restaurants that always go easy on the chili, I'll definitely ask for five stars.
I love spicy food but Thai is my weakness. I love it hot a least 5 stars.
I have one thai place that I eat at and I do 2 stars with the usual cook and 3 stars when his wife cooks. My ex husband could only do 3 at this resteraunt when everywhere else he always did 5 stars. I guess it just depends on the cook.