As you have already sent the money, I guess you are going down this road anyway, so it will be interesting to hear how it goes.
There has been a well established trade in the sort of practices you mention and it does not seem to have caused problems for those with the right contacts.
However the attitude of the Consung offices that handle the registration changes, is definately tightening up. Here in Kohn Kaen, I have successfully transferred a couple of bikes into my name, I am fairly sure two of them, a CBR400S and a Honda AX1, had restamped frames, they went through the inspection where the guy takes a tracing on masking tape, and checks with the book of the frame and engine numbers.
However I am now having problems, still not resolved after 6 weeks, with a Yamaha 250. I tried the same process as before, completing all the paperwork properly, and going to the Consung office, (Local transport office where the do the driving licenses and tests as well)
The first thing they do is request the province the bike is registered in moves the responsibility to them, if you are in the same province as the bikes current registration then this not needed. This takes one week. All seemed OK. My bike was registered in BKK, where the bike had been bought from a BKK well known shop.
Went back after one week, already stamped move of province in the back of the book. Then the guy inspected the bike, he spent a long time looking at the frame number and went back to check all his records, finally found what he thought was a genuine Yamaha number and then showed me the difference in letter shape and stamping spacing. He said not original number cannot do. He gave me all the paperwork back told me to take to the office they would consult Bangkok.
Before going back to the office, I made contact with the guy who sold me the bike, he put me in contact with the original shop, the shop said send it all to them they will do. So I left the Consung withthe paperwork including the book and sent off. Still waiting, the shop owner now thinks he will have to come to Khon Kaen, my wife tried to politely enquire in the Consung office if a little money was required, but noone picked up on this.
What I should have done apparently is sent all the paperwork back to the shop and never gone to the KK office. The registration would have stayed in BKK, but it would be in my name.
Sorry this is so long, but it appears that you may be OK in some provinces but not in others. The guys who check the numbers see many many bikes, they know what numbers belong to what type and model of bike, A real Platinum number will not be the same as a Honda XR number, so unless you can find someone to turn a blind eye, may be a problem.