If you make it to the monastery of 1000 Buddhas, you could go one extra stop on the MRT and go see some horse racing at Sha Tin racetrack. Live racing occurs on Sundays and the MRT makes a special stop at the track (but only on racing days).
The admittance fee is $10HKD (about $1.25 USD) so it really isn’t going to break the bank. Also, as a tourist, you’re able to gain special access to the tourist zone which has its own seating area as well as betting windows and on a humid day, it’s nice to be indoors where the AC is working.
Unfortunately I was there when it was raining and combined with the sheer size of the racetrack, it really seemed like there was no one there. I will say it was fun to at least check out.