That’s it. TM16 is the blue book and TM17 is the white book. TM15 is presumably archaic and now redundant because anyone entitled to it is long dead, if it was really for those who arrived before the first Immigration Act of 1927.
i think the red books may actually pre-date the 1927 Immigration Act. There were large waves of Chinese immigration since the late 19th century when British and German shipping companies started regular coastal steamer services around China and SE Asia. The government must have issued a law requiring Chinese and possibly other nationalities to report to police stations and be issued with a red book. It might not have included Indians, Burmese, Malays who were all British, or Indochinese who were all French because the Europeans, Americans and Japanese were not subject to Siamese laws under the international treaties that were the forerunners of the only surviving one, the US Treaty of Amity and Economic Relations. There was definitely a big triad criminal problem on Thailand and SE Asia and Siamese police needed a handy way to identify and control Chinese living in their precincts. It was probably like getting a Thai driving license without test by presenting a foreign driving license. Just show up at the police station with your Chinese documents and be issued a red book.
So, from 1927 I am speculating that Chinese already registered before the Immigration Act came into force could take their red books along to a spanking new Immigration office and be issued with a TM15 book of whatever colour automatically without having to go through the PR application process and prove they had a profession or trade to support themselves with. There was a similar provision in the first Working of Aliens Act in the early 70s which introduced work permits. Those already working and with PR were issued with lifetime WPs, valid as long as they remained in the same profession. It may have been a different colour too. Thailand loves to preserve archaic and redundant provisions which no one fares clean up or it just occur to them they are redundant.
if there any really old hands out there with a TM15 certificate of residence, please post a pic of it and let us know what colour it is.