Would be grateful for some quick advice:

My travel agent tells me that the minimum connection time in SGN (Ho Chi Mihn City) is 2 hours. I am asking him to book the following two flights:

Sunday, 11/18: LH772 BKK->SGN 4:05pm-5:40pm, then VN328 (Vietnam Airlines) SGN->DAD 7:20om-8:30pm

The above gives us 1h40m to connect. We will be traveling First on LH and Business on VN. Stas on LH772 indicate that it is 63% on time with an average delay of 18 minutes.

What sort of customs/immigration formalities (if any) do we have to undergo in SGN if our ultimate destination is DAD (Danang)? Do we have to exit and re-enter security? Do we get any "fast track" access for First?

Thanks very much for any help!