As a cyclist both recreationally and professionally, I have found Thai drivers quite willing to share the road with bicycles. Granted Bangkok and Patong (on Phuket) are not bike friendly, but most of the rest of the country is. While dedicated bike paths are not common, they are slowly starting to appear in areas around the country. Your referenced article in the Bangkok Post was obviously written by a car commuter not a cyclist, picking on small issues ignoring the fact that the bulk of that 184 kms will be great riding.
But one big thing is, that as a foreigner, you have to learn to go with the local flow, you can't expect the same conditions as in a bike friendly country like the Netherlands or Denmark. There is a lot of give and take, the concept of "I HAVE the right of way" becomes more "can I go first".
Similar driving attitudes prevail in other central SE Asian countries (Laos, Cambodia, Myanmar). Vietnam unfortunately inherited the aggressive Chinese driving style.
Finally a rant ... sidewalks are NOT bike paths unless specifically marked as such. Bikes are vehicles by law in most every country of the world and as such are required to use the roadways unless a specifically designated off road bike path is present. The existence of a ramp at the curb does not equate to that sidewalk being a bike path. That ramp is there for handicap access.