Week 4 claimed that อร่อย does not mean 'delicious' but 'to be delicious'. Comparison is where that claim earns its keep.
French builds a comparative out of four pieces: être, plus, the adjective, and que. Thai adds one word after the verb and changes nothing else, because there was never a copula to conjugate and never an adjective to modify.
- แพงpʰɛːŋ
to be expensive
- แพงกว่าpʰɛːŋ kwàː
to be more expensive
- แพงที่สุดpʰɛːŋ tʰîː.sùt
to be the most expensive
- อันนี้แพงกว่าʔan níː pʰɛːŋ kwàː
this one is more expensive
It takes everything a verb takes
Because แพง is a verb, it negates with ไม่ the way a verb does, it takes the intensity particles, and it can be a whole sentence on its own. No French adjective does any of that without a copula propping it up.
That is the test to apply when you are unsure: try negating the word directly. If ไม่ in front of it produces a sentence, it was a verb.
- ไม่แพงmâj pʰɛːŋ
not expensive; it isn't expensive
- แพงจังpʰɛːŋ tɕaŋ
so expensive!
- ไม่ค่อยแพงmâj.kʰɔ̂j pʰɛːŋ
not very expensive
Where the copula does belong
เป็น is a real verb and it does exist. It links two nouns: I am a teacher, this is my friend. It never precedes an adjective.
Inserting it there is the most audible French and English error in the language, and the fix is not a rule to remember but a reclassification: stop filing these words as adjectives.
- เป็นครูpen kʰruː
to be a teacher
noun, so เป็น is correct