NEEDING IDEAS FOR 'THIEF' SKILLS

Disarm (or) Gank : Steal enemy's weapon. This would require you to event every armed enemy though.
Smoke Bomb : Either a replacement for your Flee idea, or an attack skill for nerfing enemy stats / inflicting blind.
Hide : The thief disappears. Give him the Evade Physical condition. Follow it up with...
Backstab : The thief reappears and does uber damage to the selected enemy.

You could also use map-related things, like locked chests and secret passageways. Compensate for the annoyance of having to drag him everywhere by also making him capable of making Skeleton Keys or whatever. Maybe this is a dumb idea.

Is this for Runic Cipher?

Kick (in the nuts) - has a chance to stun humanoid targets?

author=Jude
Poisons are a staple thief ability. Have them apply to normal attacks for a duration. Different poisons, different effects.

^ that

although some could argue poison is more for assassins, thieves still use it.

Let the thief's implied natural luck effect the battle in other ways.

Jinx -This ability that causes enemy attacks to malfunction while active.

Rabbit's Foot - Skill give the party guaranteed first hits against slower monsters. It might even turn on a switch that randomly causes disadvantages to the enemy in battle. Fighting in a cave? The thief is lucky enough that rocks fall on the enemy.

Surefooted - They don't take certain types of terrain damage, and/or they do not set off mechanical traps.

Weakening Strike - The thief has an attack that reduces the target's resistance against a weapon/damage type used by other players.

Attack of Opportunity - Event it in such a way that after every party member attack, there is a percentage chance that the thief will tag on an extra hit to rack up more damage. (Not hard to code into the DBS, actually.)

Expert Dodge - The thief uses a status on him/herself that causes them to evade all normal attacks. To offset its power, cause it to drain MP each turn, and make Defend (or something similar) clear the status. Useful if your enemies actually use normal physical attacks, not so much if they don't.

Keen Vision - The thief reads the enemy well enough to tell what attack they are about to use. This gives the whole party boosted defense/raised defense against certain attributes, for a time.

Ok,I'll teach you *Clears throat(Oh yuk! last night was still in my throat!(Just kidding:P hope you did not get disturbed :P))*

What we'll need:
1.A spare skill
2.A switch
3.A variable
4.Items to be stolen
5.Switches for the monsters

Make the skill "Steal" into a switch activator,Example let's say Switch name is steal.
Now go to the monster groups and make a new event.
In the new event, make a precondition which requires the switch "Steal" to be ON.
IN that event, select face<Blank>(OR of a character if you want)and make message with choices,Example:Who do you want to steal from?
Monster1<What ever name you want to give>
Monster2
Monster3
Next>(For the rest of the monsters on the field if there are more than four)
Prev<
Monster3
Monster4
Next>
Prev<
Monster5
Monster6
Next>
Prev<
Monster7
Monster8(According to how many you have)
And then, In the choices,you edit what happens, like Show battle animation<Or none if you want>and then put a variable to work, let's name this variable "Stealing".
In this variable, you set it to go random between a few numbers<According to how many items can be stolen an an extra one for not able to steal anything which might preferably be 0>Now make conditional branches, IF variable "Stealing" is Equal to 0 then show message,Failed to steal!(OR what ever you want it to be)
And then you TURN OFF the switch so that the even will not repeat it self.

New conditional branch:IF variable "Stealing" is Equal to 1 then show message,Stole potion!(OR what ever you want it to be)and enter item management and change our items to +1 potion.
And then you TURN OFF the switch so that the even will not repeat it self.
And so on, And so on....(Conditional branches according to what number you chose.)
IF you want the character to be only able to steal 1 item from a selected monster,
then you should make switches=Monster1,monster2......monster8
which are activated by another battle even which starts at turn 0x0.
You can edit it to be as soon as an item is stolen from the chosen monster,turn switch Monster1(OR any selected monster)OFF.

I hope i helped.(Tell me if I am missing anything)

EDIT:
Thanks Trihan!
Ok,IN every choice other then Next> and <Prev, You put a conditional branch with an "Else handler",

If monster<Insert monster here> is able to act:
(Insert stealing event)
Else handler:
The monster is<Dead or what ever you wanna say>.

Steal .... stuff
Stealth
Hide
Knife throw
Poison
Sleep
Blind
Smoke bomb
Luck