Flats might be better to begin with. I've done Bali and parts of Malaysia on drops, which fine but never toook the lower position, mostly because I needed to see the unexpected, apart from other motorists. Nothing like rounding a corner to see a family of apes heading towards you the other side, or, in Australia, a wild boar come crashing across the road in front of you.
The biggest problem had in Cambodia on the most recent trip was being too ambitious about distance at the start, and finding the heat got a little too much close to mid-day. when I still had a fair way to go. I should have know better, of course. The other was English - not much spoken the further you are away from Siem Reap or Phnom Penh, and that includes the hotels.