Likewise, I would have just paid the 1500 and chaulk it up as a lesson learned. It sucks being lied to or cheated, but best to not risk trouble with the police in Thailand or any foreign country. You have no protections so be smart.
MK in Siam Paragon is one of my favorites in BKK. I love their roast duck/roast pork/ crispy pork plate. I enjoy the street foods/stalls, but I also enjoy the A/C inside the malls.