You’re almost correct, girl.
You might think of the present continuous tense in English or a situation continually happens, we use ‘still’ to emphasize that situation still happens. This is the same way we can use ‘ยัง’ in Thai
for example;
1. (like you say above) ฉันหิว becomes ฉันยังหิว. =>you’re continually hungry, no matter whether you’ve just eaten something or you did not eat something before.
2. Someone is trying to explain something to you, and you want to tell him that you still don’t understand what he is explaining. You may respond to him in Thai ‘ฉันยังไม่เข้าใจสิ่งที่คุณอธิบาย’
‘Yet’ and ‘not yet’ is basically used in the similar way in English when we make the negative and interrogative sentences in the present perfect tense form (or present tense form)
For example.
1. when you ask your mom that “Has dad arrived yet?” In Thai “พ่อถึงหรือยังค่ะ/ครับ?” And your mom may respond you that “dad hasn’t yet arrived” in Thai ”พ่อยังไม่ถึง”
2. my boss ask me that “Have you finished that project yet” in Thay “คุณเสร็จงานนั้นหรือยังค่ะ/ครับ” and I might respond that “I haven’t finished yet” in Thai “ผมยังไม่เสร็จครับ”
Hope you get the idea and feel free to ask if you're still wondering.
[หวังว่าคุณจะได้แนวคิด และรู้สึกสบายใจที่จะถามถ้าคุณยัง(still)สงสัย]