Bike is from the states. Had it 20 years. Always a pain to find tires.

size = 700 x 35

Tried Jacky and Arm and a few other. Nobody had one and nobody thought they could order it.

Any other shops to try?

It's a pretty common size for touring. You could try Chaitawat but, you will probably have to order it from overseas. eBay it and have somebody mail it to you.

Look for Kenda tires model "kwest" . I run them on my in town MTB in 26x1.95.

I couldn't even get any of the shops that I rang to order me a tube for a 22" mb tyre... Basically they don't seem interested in anything other than the super common Thai sizes.

I ordered what I wanted off ebay. Delivery prices not too bad if you choose carefully; about two weeks average delivery from UK.

When I have ordered bike parts I used Fedex. Driver collects the duty , believe it is %30. If it is mailed to you how would the required import duty be paid?

I have very good 700 x 35 heavy duty street tires on my Trek bike, bought at Song Bicycle on the moat.

http://a.northernthailand.com/chiangmai-shops-a-services/bicycles-shops/484-song-jakayan-bike-shop.html

When I have ordered bike parts I used Fedex. Driver collects the duty , believe it is %30. If it is mailed to you how would the required import duty be paid?

If you get them to send normal registered mail, tax will either be nothing or 7% IME. Couriers always make a mint in league with customs here - well documented, search here and see what people say about the rip off charges from the large courier companies. Worst case is they hold it at the post office and you go collect it and pay any charge - will be less than 30% for a small package like an inner-tube. Get stuff every now and again (under pants for example - can't cope with Thai nut-squashers - cotton socks too), pay either nothing or 7 baht for a shoe box size box stuffed full. Registered mail, never lost a package.