The 1921 Railway Report refers:
A Halt Station was opened at Ho Mun Tin, mile 2¼, where the local morning and evening trains call for the convenience of a new community which has lately settled at this point, and a temporary platform built of old sleepers was provided. This is not an ideal site for a station and will probably not be required when the road trams serve the neighbourhood, as is anticipated will be the case in the near future.
It is difficult to locate this station as it doesn't appear on maps. The only information is that is was located at "mile 2¼". I printed a 1924 map from hkmaps.hk that has a scale on it. Then I used an (old fashioned analog) opisometer or map measurer to locate the spot 2¼ miles from the start of the tracks. This is very close to todays Waterloo Road. Of course, 2¼ miles is a bit imprecise and probably allows +/- 200 yards (1/8 mile). Also the opisometer method isn't too precise (used the average of a few runs).
What makes me confident of the correct (approximate) location is given on the 1920 map on Gwulo. North-east of the tracks is a village labelled Ho Mun Tin with a couple of buildings. Again, not a proof, but a good hint.
The existence of this stations surely wasn't long.