I just changed my CRF250 oil for some 15/40 PTT Semi Synth I bought at Sangchai Panich Honda on Kheow Nawarat Rd for 80Bht/Litre. The bike is running noticeably quieter and smoother than after only @2500Km on whatever the guy who converted it to 300 put in. In fact better than it was immediately afterwards!
They are doing PTT Full Synth for 200Bht/Litre and I bought some to try later.
There are lots of oil dealers in Charoen Muang Rd, mainly car oil but consensus seems to be that's OK as long as it doesn't contain 'Energy Conserving' friction modifiers.
Tests have shown that Mobil1 is the best oil out there but if it's four times the price here I would rather buy the best domestic alternative and change twice as often.
Manufacturers change intervals are as much of a joke as Microsoft Laos maps - 12,000Km in the service book for the CRF - wtf! Tests show most normal oils are breaking down by 3000miles, synthetic lasts twice as long or so.