Hi there,
You can get the Chatmessage content using :
ex : CHATMESSAGE 21 BODY Hi, what's up?
Now to get the history you could request to get chatmessages from/to the target user :
SEARCH CHATMESSAGES [<username>]
This is a work around. I reckon that a "OPEN CHATHISTORY" would be better that why I invite you to post an new feature in Jira.
https://developer.skype.com/jira/browse/SPA
and people will vote for it I guess.
Thanks,
Antoine