I’m going to BIGBANG’s concert in Bangkok and I’ve never bought concert tickets before..help

Hey, thank you for reading this, I just have two question.

first, if I bought a membership card (via b.stage) can I buy 2 tickets with it??

Cause I’m going with my mother and I thought it’s one per person, so now I have 2 membership cards.

second, if I buy seating tickets, do I have to sit…???