Patrick you are mostly right, but also the Army version is made from Type 38 rifles.
The rearsight has been heavily modified, ladder cut in 3 peices, middle part thrown away and the remainig two pieces weldet back together. Also the sightbase has been modified to fit the "new" ladder. So it looks like a T38 carbine sight, but the graduation of 24(00)m is still there.
I will keep looking for the Army versin too, or bette I will not look for it, that makes stumbling across one much easier
The US "missed" the surplussing of the Thai weapons, the import ban from 1968.
The batch was small, baut I spotted any known variation of Siamese/Thai Arisakas here over the years.
Chris