Hi Ray,
I guess what you are looking for is a jacket with armour in the impact zones, but also good ventilation. I bought my Richa jacket in the UK, it has two removable liners, one for water and one for warmth. It is well ventilated if you take them both out, but last few weeks the warm liner has been in most of the time. There are similar jackets over here.
I have seen two places in Udon, One shop has a very large cardboard box full of well priced jackets and trousers, I think the guy is called Jimmy, Thai guy, if you go down past the Irish Clock, away from the Udon night and day end toward the main road, it is a few meters on your right, next to a shop with Tuk Tuks in. I am sure you will know it.
The other place is a clean well set out shop with some nice clothing, called Tech 21 shop, Thai guy speaks English, called Keak, his phone no is 0895725656. I have been to the shop but cannot give you directions.
Not much here in Khon kaen, Bangkok certainly has a few shops with what you want.