Den. Ueang Pheung (Den. jenkinsii x Den. aggregatum)
A reliable bloomer. Needs complete neglect between Nov - March. Very bright light to almost full sun and cool temp during winter rest. Heavy watering and fertilizers during growth period.
@oscar
The plant is tiny in a 3 inch pot in sphagnum. I'd say no taller than 5".
I leave it out to defend for itself between Nov and March. No water, except for a sprinkle here and there during our rainy season. Also practically in full sun during that time.
Next to it is a rat tail cactus, it's companion plant.
Picture below.
Andrew