You don't need STR & INT. Alright, your lvl doubles your dex.
This is for normal thief.
Example:
- I'm lvl 15 and my DEX is 30.
- I'm lvl 21 and my DEX is 42.
- I'm lvl 25 and my DEX is 50. And so on...
Do this build to Lvl 42. And start going 1 DEX and 4 LUK.

This is for who wants to be STR bandits:
(You can use the one above, or this one.)

Level STR DEX INT LUK
20 10 40 4 67
25 15 50 4 77
30 20 60 4 87
And leave it like that. >.>

Thief Assassin Skill Build:

MAX Nimble Body
MAX Keen Eyes
3 Disorder
10 Dark Sight
MAX Lucky Seven

Thief Bandit Skill Build:

MAX Nimble Body
MAX Double Stab
3 Disorder
18 Dark Sight

Assassin Skill Build:

MAX Claw Mastery
MAX Critical Throw
MAX Claw Booster
MAX Haste
Extra Points in 3 Endure then all in Drain.

Bandit Skill Build:

MAX Dagger Mastery
MAX Dagger Booster
MAX Savage Blow
MAX Haste
Then rest of the points in Steal.

Hermit Skill Build:

MAX Meso Up
MAX Shadow Partner
MAX Avenger
MAX Flash Jump
MAX Alchemist
Extra points go to Shadow Web.

Chief Bandit Skill Build:

MAX Assaulter
MAX Pickpocket
MAX Band of Thieves
MAX Chakra
MAX Shield Mastery
3 Meso Explosion
If you have extra points put all in Meso Guard.