French gives you two options and one of them is safe with anybody: vous is never wrong, only sometimes distant. Thai has no vous. It has a large set of terms, every one of which asserts a specific relationship, and the closest thing to a default asserts distance.
คุณ is correct with a stranger in a formal setting, with a customer, on a form. Used with the neighbour you have had for two years it is cold, in roughly the way vous would be once a friendship has formed and there is no tutoiement available to move into.
- คุณkʰun
you (formal, and distancing)
What replaces it
The kinship terms from week 3, the person's name or nickname, or nothing at all. In ordinary conversation the age term is doing the work almost all of the time.
Guessing an age wrong is a much smaller error than reaching for คุณ, and erring older is the safer direction.
- พี่pʰîː
you, if they are older than you
- น้องnɔ́ːŋ
you, if they are younger
- ลุงluŋ
you, to a man of your father's generation
- ป้าpâː
you, to a woman of your mother's generation
The first person is easier, but not free
ผม is safe for a man everywhere and stays safe, so half the problem does not exist for you. It is only slightly stiff in very close conversation, where Thai men often use their own name instead.
The rude registers exist and you will hear them between friends. มึง is in this course to be recognised and not produced: a foreigner using it reads as having learned Thai from one specific friend and nowhere else.
- ผมpʰǒm
I (male speaker)
- ท่านtʰâːn
you (respectful, for rank)
monks, officials, the very senior
- มึงmɯŋ
you (rude)
recognise it; do not use it