Time to throw another in the mix
Many will be aware of the Maeklong Railway in Thailand where market traders have to collapse their stalls to allow the eight trains a day to pass on the last mile to the Maeklong terminus. Someone has even made an HO model of it with collapsing stalls. However the railway has a longer history than as a 21st century tourist attraction, and some stuff is still around to form the basis of a layout.
The Maeklong railway is actually two railways - the Thachin Railway from Bangkok to Mahachai and the Maeklong Railway from Ban Laem (on the opposite bank of the river from Mahachai) to Maeklong. The companies merged sometime early in the 20th century and were nationalised after WW2. Like the rest of the Thai railways they are meter gauge.
In the early years the railway was operated by two classes of small tank locos built by Krauss, examples of both still survive as static displays.
The 0-4-2T were originally for the Thachin Railway
and the 2-4-0T were originally for the line to Maeklong though they were apparently all used on both lines and similar (or even the same) locos appeared on the Pak Nam railway East of Bangkok. (The TRC loco is now repainted and on display in Pak Nam)
Drawings of both were in Continental Modeller a few years ago
As for passenger stock, we might have to guess. Something like this 4-wheel coach now in use as a children's library won't be too far out
And for goods stock, this old van receiving a bit of TLC at Mahachai works is probably an old Thachin Railway original
This might be a suitable layout for doing in S-scale (1:64) on 16.5mm gauge track. I'm not an expert in HO ready to run but I'd guess there are suitable small tanks with the right wheel base to form the basis of the loco types