I've got a good chair with a pneumatic gas cylinder that is wearing out.

It's good news that we can actually buy replacements for these things instead of having to replace the entire chair.

I can by one online and import it,

(example, http://www.echairparts.com/servlet/the-Pneumatic-Gas-Cylinders/Categories)

but I'd like to find a seller in Thailand if I can.

Anybody know one?

Timely reminder as mine has started to go South (down) so just used that site to order a replacement - very easy to use and shipping was $19.95 so not too bad. Have had very poor luck with locally sold chairs so a bit less than optimistic that local replacements would be good for those at 90kg or more. Find recommendations to soak with WD-40 for a day before trying to take apart unit on chair.

Personally I don't need to actually be able to move it up and down once I've got it adjusted, so a fixed-length bit of rod welded to fit worked for me, total cost 350B - but I've gotten to know a few of the shops in the engineering shophouse neighborhood around the corner from me, might be a little more than that for others.

I've found sourcing parts like that so difficult it's usually cheaper to buy a new product, if you value your time that is.

Yeah, they always die before the chair.