For boots try the boot maker on Chotana Road, Chang Puak, opposite the Teachers College. I've had 2 pairs made there for 3,500 baht a pop and they are good. I get 12-18 mths out of a pair with heavy, almost daily, use. Sorry don't know the name of the shop, (its a bit of a no-name shop.)
For a leather jacket try New Boonkrong Leather, on the Sankamphaeng road, on the right hand side going out. From what I can gather they should be ok. I'm lining up for a new jacket there in a couple of months. I expect cost to be 6-8,000 baht price range with a bit of luck = local non-tourist price. My previous (current leather jacket) cost me 3,500 baht 8 years ago & was made privately by one of the guys who worked at New Boonkrong, but he is no longer around.
Hope this is a help – let me know how you go.
Downstairs in Carefore there is an army type shop, the youngman (keen biker) that owns it, now and again he picks up the odd large biking leather from Chat-tu-Chac market in BKK, don't bother with Cha-tu-chac yourself as you'll be wandering around all weekend looking. Starting at 2,500BHt (Thai price) he's also got some boots in. I bought some steel toe capped boots on the north corner of Chaing Puak Gate -800bht well happy with them.
Dave- Had a shock walking into Charts new place last night, amazing!