I just stumbled across your post. Osaki is a company based in Thailand that manufactures chains and sprockets for motorcycles. The red arrows that you've come across indeed mark an offroad course. Osaki is one of the main sponsors of the north thailand enduro championship and as such the race marshals set out the course using red arrows printed with the 'Osaki' brand name. We are also obliged to display the Osaki stickers on our bikes on race day.
No, enduro races in Thailand are not based on roll charts, which IMO are only used for rallyes. Here in Thailand the organizers apply the (european) enduro system, where the course of both specials and liaisons (in different colours) are set out with direction markers (arrows and crosses) and attention/danger markers (single, double, triple exclamation signs according to danger level). So no roll charts available, but you might stumble across the course markers when going offroading.
Last saturday Big&Tall, SuzukiLuke and I followed part of the course set out for a race that was held in december (and in which I had to pull out after a crash), most of the arrows were still in place. This time we also had to 'pull out' after Big&Tall succeeded in flipping himself over the handlebars when the front wheel of his KLX disappeared into a sink hole when crossing a river, completely drowning his bike (and almost himself and his rescuers) in the process...
There are only set times for the liaison sections that participants need to respect and for which they get penalized if showing up late at the start of a special. No set times for the specials, where everyone goes flat-out balls-to-the-walls T.W.O.!