เจอกันใหม่

Yes, as long as you add 'khrap' or 'ka' at the end. For an even better impression, use 'พบกันใหม่ครับ'.

'ใหม่' means new/anew, while 'อีก' means again. In this specific phrase, 'ใหม่' is the standard idiomatic choice.

Absolutely. It's very common to end a phone call with 'โอเค เจอกันใหม่นะ'.

It's just a shorter, more casual version, similar to how English speakers say 'See ya' instead of 'I will see you later'.

Only if you actually expect to see them again. If you're just leaving a shop, 'Khop khun khrap' (Thank you) is more common.

Yes, it literally means 'Meet each other anew'.

Just use 'เจอกันใหม่นะ' without a time word. It's perfectly fine.

In a casual email, yes. In a formal business letter, use 'หวังว่าจะได้พบกันใหม่' (Hope to meet again).

Yes, 'เจอกัน' or 'ไปละนะ' (I'm going now) are the most common casual ways to leave.

It's a low tone. Imagine your voice starting at a medium pitch and dropping down as if you're disappointed.

Yes, it's the perfect way to say goodbye to people you've just met and liked.

Rarely. You'll hear it in movies when someone is dying or leaving the country forever.

The most common reply is simply to say the same thing back: 'เจอกันใหม่ครับ/ค่ะ'.

Not with close friends, but with anyone older or in a position of authority, a Wai is highly recommended.