I see there has been a feature request made for i3 as a default profile in the Cendio bugzilla:
https://www.cendio.com/bugzilla/show_bug.cgi?id=7570
In the meantime, though, it should be pretty straightforward to add an i3 profile stanza in /opt/thinlinc/etc/conf.d/profiles.hconf manually. The parameters are described here.