How safe is cycling as a commuter in Bangkok?

I've seen other posts that say cycling is basically impossible in Bangkok because of the traffic and bad pavements, but I checked my route (Imperial World Samrong to SBU) and the pavements seems to be wide enough, they don't look too bad, and there's not many parts where I would have to cycle on the road.

Would cycling in this case be worth compared to just taking the BTS (I'd like to save some money)? If anyone knows a good cycling route to SBU, then I would like to know.

Also, this might sound a little dumb, but are there any licenses or registration fees to ride a bicycle? I don't want to be doing anything illegal.