thanx You cant , you need to take some levels of an arcane class to qualify for palmaster (needs 3 levels wiz/bard or sorcerer).

Syrath 20 palemaster tends to be a bit restrictive (some ac bonus; but two levels where you will get none).
16monk pre-epic
4 bard pre-epic
[the above assumes a melee character; your base attack will be identical to 20 monk levels pre-epic]
19 palemaster [get epic mage armor and warding, if desired]
1 bard (max umd; tumble)

Or not; I'm not good at the building thing, still learning myself. If you took wiz level instead of bard you would be able to cast spells up to a level 11 wizard if you can get the scrolls to memorise. Bard is probably better though (UMD you can cast any scrolls)

Syrath My favorite Monk/PM goes like this: 14 lvls Monk, 5 lvls Wiz, 20 lvls PM, 1 lvl monk. I prefer Wiz over Bard for the extra spellcasting ability, besides you get tumble as a Monk class skill as well as Bard. You don't have the max ab possible with this build, but you will have pretty good AC, not to mention epic spells.
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If everyone is thinking alike, then someone is failing to think. Only issue with the Bard is that it would require an alignment shift. Monks have to be Lawful; Bards must NOT be Lawful. So unless you have a way to shift along that axis, I would go with Wizard instead.

As for Monk 20/Wiz 4/PM 16, you can certainly do this; you'll be able to get Epic Spells and up to 6th lvl arcane spells, but you'll only have 4 caster levels, unless the world you're playing on has fixed the PM caster lvl bug, or unless you're playing with the PrC.

I would probably go Monk 20/Wizard 10/PM 10, as this will give you a decent caster level and let you cast up to 8th lvl spells. Monk 18/Wizard 12/PM 10 would let you get 9th lvl spells, which are nice, but then you would lose 1 point of BAB over the previous build.

Also, if you decide to take a decent # of Wizard levels, I would pick up the Extend Spell feat so that your buffs will actually last a while.