There's an LhA GUI on Aminet. Or I think DirOpus used to unLhA. I know my custom DiskMaster setup does, too.
But, really, out of all the commands for LHA, all you really need to know is.
lha x
ex:
lha x ram:blahblah.lha dh0:blah/
would extract file blahblah.lha to the directory blah on dh0:.
[edit - fixed command] Right you are, Piru. I've been using Linux too long. I want to qualify everything with a - or / . ;-)