Radeng, just curious. Was the insulin in Pens, or in small bottles with associated syringes and needles?
I've transmitted BKK a number of times with Pens (two types) and have never been questioned there.
In fact I have never been asked to produce my prescription anywhere. It probably wouldn't be much use to someone who doesn't understand French. It does look very official though!
Take it with you, you will never regret doing that.