It's one of th saving throws that comes up relatively often, so I would at the very least keep it at 10 to not have a penalty there, just like it's advisable to not have wis lower than 10.

Rogues only really need DEX maxed out, so no reason not to grab some hitpoints, especially for the early levels. Don't leave any stats on an odd number btw.

I play most of my games on Tactician and Honour mode so I always set Constitution to 16 on every single character I create. I believe Constitution is the 2nd most important stat after the primary stat for any class.

thanks all, Ill aim to 10 then ;)

there is a game mechanic that only allows the interacting character to make saving throws for group "discussion/discovery" encounters (even though a better qualified specialist may be in the group for things like "aracana")

so, whatever your lead character is - meaning the character that is first into the room - then during any encounter dialogue, this character will need to be making "checks" (saving throws) for everything from intelligence, wisdom, and charisma.

so, in this one crappy mechanic, the game does force us to consider at least increasing our character's charisma to help with persuasion checks (which can make a huge difference in how the game plays out)

maybe something to consider ?

and related to question, i had con at 10 and str 9 for starting my thief

Nah, you're going to want some CON when those nasty CON saving throws come your way.

Dex is the priority as this will help your AC, your damage, your dex saves, and basically every ability check the rogue would want to make.

Then it really comes down to your priorities. I usually like having some extra Con because I don't like dying. Other people may have other priorities.

Even if your rogue always stays at range they might get ambushed/teleported to or hit by some nasty spell so some extra hp never hurts. :p

Honestly, outside of role-playing reasons to do otherwise, I think there's a solid argument for giving pretty much every character at least 14 CON.
Sure, you'd rather your rogue not get hit, but realistically it's going to happen from time to time, and you want enough HP to take a hit or two and keep going. Plus, as people have said, Constitution saves are one of the most important ones.

At start 15 dex+2, 15 con.
You can put the rest into wis for saves or strength for some shoves and jumps (lots of heights in bg3).
Intellect is useless (u can wear ogre crown) and charisma is better covered by a charisma-maxing class (paladin, sorc, bard, warlock...).
Most classes in bg3 really have only 3 useful stats, the other two can be dumped.

con is something I would never use for a dump stat, but I don't see a rogue ever needing it to be high.

For a rogue, my beginning stats would be:
STR - 10 (for those basic jumps)
DEX - 16
CON - 16
INT - 8
WIS - 14
CHA - 10 (no penalty in social situations)

Then max DEX at 4 and 8 and you're sitting pretty. Also solid stats if you wanna bring in 5 levels of ranger for extra attack, which is a huge DPR increase.