As i know index s a local brand, which i wouldn't suggest you to use on a big bike. if you having headaches u must be wearing a wrong size helmet.
there s a nice helmet shop in MBK Shopping Center Bangkok, here s a link of their website www.ridersdna.com
i hope that helps.
thanks for tips, i was in MBK / bangkok for the riders DNA helmet shop, they got tons of airbrush painted full face and open face helmets, one of the coolest helmet shop ever been, Bought a shark Raw (nearly half price of Europe, alot cheaper than where i live).
anyway go on and ask for discount, don't forget you are in Thailand))