No they wouldn't. In the UK if people know you're from Thailand your Thai. China Chinese, Japanese etc
Certainly wouldn't be called out as Asian on TV. Thai food, Chinese, Japanese..not Asian food. The list goes on and on. Aharn Farang. No differentiation attempted at all. Total ignorance and bliss.
We call Germans, Italians, Dutch by their nationality not European. If you called someone from New Zealand an Aussie and found out it was wrong you'd never do it again.
Whatever its roots and connotations it should change in this day and age considering the volume of different nationalities here.
I've heard elderly people call people derogatory names out of naievity. No offense meant but doesn't mean it shouldn't be stopped.
Totally wrong.