We rented a car from our car salesman's cousin. Sounded great, nice car, no written contract. Paid the ten days I needed in advance. Nice people but when we had a problem with the car it was all on us.....ran into a pothole, ruined a tire and broke the plastic radiator housing putting the jack in the wrong place. No other car available so ended up getting the car fixed myself....7,000 baht out the window (fortunately our condo Manager helped me get it fixed.....the rental guys didn't even bother to come and look at it).
Anyway, sometimes no rules is great. Sometimes it bites you in the rear. Next time I'll use a big brand rental company.