Where in Bangkok can I buy urostomy supplies,, preferably Convatec. I have searched the internet with no success, I know some of the big pharmacys must stock them. Any help would be appreciated.

I would give Bumrungrud or one of the other big hospitals a call.

Follow-up:

I looked up urostomy and then

http://www.bumrungrad.com/en/search-for-a-thailand-doctor

I see they have specialists in urology, nephrology and urogynecology which I guess are related to urostomy. If you can get a Thai speaker to call the dept. then the nurse assistants might be able to point you in the right direction, otherwise just pop in and ask to speak to a doctor (the docs all speak English but it's hard to get a hold of them through the hospital line).

Good luck!