(Do note that the following information was taken directly from the transportation department. However, it can vary from a place to another. It is always the case in Thailand).
This is the official form from the government to transfer a motorcycle: http://www.dlt.go.th/th/eform/files/ins_car_trn.pdf
1. You will need the registration book (green book). The owner must signs in the bondholder indicated area.
2. A transfer request and transfer acceptance forms (use the forms of transportation department only) along with a copy of identification card of the transferor and the transferee and certified the copy. For foreigners, they need to show passport and often a work permit**.
Notes: If the transfer is between spouses (you will need the marriage certificate and certified the copy by both parties) do will not have to pay the transfer fee appraisal but pay around 105 Baht transfer fee
** Do note that a work permit is NOT a requirement. However, foreigners must show a proof of address and the transportation department often ask for that document. A yellow ta bian baan (or yellow house book) can also be a proof of address. Another way is to get what is called a "certificate of residence" from your local immigration. Lastly, we have seen people using a "police report" as proof of address.
3. Bring the motorcycle to make an inspection at the vehicle check-up. (Bring any vehicle that needs to be transferred inspected).
4. Once it is finished, wait for next step at receiving document and evaluation of the price window. Appraisal staff will review the document and when it’s done the staff will return back the document to check and receive window and pay the transfer fee.
5. Hand in the document at the inspection of documents and pay 90 baht for tax fee,10 baht for vehicle check, 105 baht for transfer fee, 20 baht for management fee. Transfer fee is based on the assessed value of the vehicle (in case you are dealing with a fee according to the Bureau of Transportation but if a husband and wife transfer due to affection is without charge).
6. Receive registration book and verify if transfer is made.
Note: In case of the property address is changed, transfer, pay for motorcycle registration fee or pay for taxed can tell the staff to change the address immediately.
You can do the same process using a power of attorney (there is a special form from transportation office) along with certified copy of identification of the transferee. That is used when a party is not present for the transfer. Again, for foreigners, they will need to show their passport and normally a work permit (or a proof of address) a stamp duty fee of 10 baht along with a copy of their identity.