Good answer Beags except ... He asked if you can be a TRI with a PPL not if you can be a CRI!
Look at LASORS H4.1 and the answer is still yes but you need considerbly more experience (1500 hours on Multi Pilot Aeroplanes and 30 sectors on type in the past 12 months). While a CPL or ATPL is not specifically mentioned it's hard to see how one could meet these requirements without working as a professional pilot. I suppose it could be done if you spent a lot of cash!
I know the original question mentioned "type" Cessna Caravan which I suppose is a single pilot type but, isn't it also turbine powered and therefore needs a type rating? So, to teach on it do I need a TRI qualification with the pre-requisite 1500 hours on Multi Pilot Aeroplanes which sems irrelevant or do I need a CRI rating or ...
Cant stand it, I'm off to bed now!!!
Happy landings
3 Point