think i've done almost all the major roads in cambodia with 26*1.95's, half before they were paved. you could probably get by with 38's nowadays unless leaving the main routes.
chinese have been paving just about everything, but quality varies. i suspect they subcontract out by kilometer sections to whoever's uncle's cousin depending on brown envelope requirements. leads to poor quality work and cutting of the corners. road surfaces don't last long because of that and the perpetually ueber-overloaded vehicles.
you wind up with alternating sections of smooth pavement, potholes, dirt, pavement..... conditions change quickly, road reports from last year no longer valid.