Well that depends, has it reincarnated twice? if it has reincarnated twice and evolved into something other than a chaos chao than you have to wait for it to reincarnate again, then do the one of...
Chaos chao dont breed at all!lol-when it's 'mating season' in one of the gardens, a chao will get flowers around it... then, either the nxt chao that walks by OR a chao you put nxt to it will like...
These are very rare chao that are immortal and never die. Get any chao and reincarnate it twice. Feed it one of every 21 animals. No chaos drives!!!!!!!!!!!! When it evoles, it will be a chaos chao!