Most taxis know the malls within Ratchaprasong, but it can be a little hit and miss. However, almost all will recognise and understand 'bpai Phra Phrom Erawan' (go to Erawan Shrine). Travelling via Skytrain is just as simple, just exit at either Chidlom (the closest) or Rajadamri BTS stations.
Within the district, only use taxis willing to use the meter and ask bell boys to hail taxis at any of the hotels or shopping centres. Ignore anyone offering to take you to temples for a "last day only sale". If staying in the district, everything is within walking distance, and the skywalk extending from BTS Chidlom to BTS Siam provides convenient access throughout Ratchaprasong from 06:00 until midnight.