here is a new thief skills hack, a little better than the previous one.

     THIEF LVL 0 1 2 3
----------------------
         climb 0 7 8 9
    sneak/hide 0 5 6 7
    pickpocket 0 5 6 7
     pick lock - 5 6 7
         traps - 3 4 5
read languages - - 3 4
  read scrolls - - 1 2

at first level, the thief can choose a specialty (any skill available at first level) and they get an additional +5 bonus to that skill.

normally, use DC15 for thief skill checks. (30% success at d20+0, 55% success at d20+5)

CLIMB
A normal stone wall is DC15. slippery walls are DC20, etc.
A first level thief has a 65% chance to climb a normal wall. A first level thief who specializes in climb has 90%  - the same as a classic D&D thief.

PICKPOCKET
the DC to remain undetected is 5 under the DC to successfully steal - so usually DC15 to steal but DC10 to remain undetected.

PICK LOCK
A character needs to take a level of thief to be able to pick locks.
A 'class I' lock is DC15, and a 'class II' lock is DC20, and so on.
A first level thief (d20+5) has a 55% chance to open a class I lock. If they choose the lockpicking speciality (d20+10), they have a 80% chance to open a class I lock, and a 55% chance to open a class II lock.

       --------LOCK------------
       I    II   III  IV   V
       DC15 DC20 DC25 DC30 DC35
d20+5  C    D    .    .    .
d20+10 B    C    D    .    .
d20+15 A    B    C    D    .
d20+20 A    A    B    C    D

A-95%, B-80%, C-55%, D-30%, .-5%

TRAPS
A character needs to take a level of thief to be able to find and disarm traps like a thief.
A first level thief (d20+3) has a 45% chance to find and disarm traps. A first level thief who specializes in traps (d20+8) has a 70% chance to find and disarm traps.

READ LANGUAGES
A character needs to take two levels of thief to be able to read unknown languages like a thief.
Reading unknown languages is DC20.
A second level thief (d20+3) has a 20% chance of successfully reading unknown languages.

READ SPELL FROM SCROLL
A character needs to take two levels of thief to be able to read a spell from a scroll like a thief.
Reading spells from scrolls is DC20. 
 A second level thief (d20+1) has a 10% chance of successfully reading a spell from a scroll.