Complaining at immigration worked for me. I was there to get my stamps transferred from my old passport to my new one. The IO officer said, before he started, 500 Baht, no receipt. I told him I wasn't going to pay as it's a free service. There was a few words exchanged between that officer and his supervisor. My passport was handed over to him and he did the transfer. No charge. My friend who was behind me and having his stamps transferred as well took my place with the original IO. No request for money. So it is right to complain.