ตาร้อน

No, it's not a swear word. It's a common idiom. However, it describes a negative emotion, so use it carefully.

Probably not. It's too informal. Use 'อิจฉา' or just express your admiration instead.

'อิจฉา' is the literal word for envy. 'ตาร้อน' is the idiomatic, more descriptive version.

Only in a very literal, medical sense (like a fever). 99% of the time, it's figurative.

You can say 'ฉันไม่ได้ตาร้อน' (Chan mai-dai taa ron).

Not really. Envy is generally seen as negative, but you can use 'ยินดีด้วย' (Congratulations) to be positive.

Yes, but 'หึง' (heung) is more specific for romantic jealousy (protectiveness). 'ตาร้อน' is for wanting what they have.

Because envy often starts with seeing something. The eyes are the first to 'catch fire'.

Only informally between close colleagues. Never in a formal report.

It's a more intense version. 'Phao' describes a burning, glowing heat.

If someone is eating a delicious steak and you are eating salad, yes! 'เห็นสเต็กแล้วตาร้อนเลย'.

Very common! Many pop and Luk Thung songs use it to describe heartbreak or social status.