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at terminal 1, you will see yellow taxis immediately right after you walk out of the building and turn left. Do not go down the ramp, that is where people go to wait for pick ups. There will be a desk where they will ask where you are going, which is for your safety as the desk would take down the taxi plate number and where they are taking you (but in actuality, no one keeps track). Either case, when you get in the taxi, make sure they start the meter. It is very important, other wise they will try to charge you double or triple the rate. The yellow taxis are already about double normal city cab rates, so do not let them inflate it anymore. Also when you mention Dusit Thani, being it is a 5-star hotel, the drivers will assume you are rich and being you are foreigner, dumb as well. So make sure you tell them to start the meter. A cab fare with yellow airport taxi's to Dusit Thani should not exceed 400 at most. Normal city cabs will be 200, so when you go back to the airport, make sure of that as well. Always tell the taxi driver to start the meter every where you go. good luck and enjoy your trip