UPDATE: The result is in! "FloridaGirl" at "Peace in the Valley" identified this mystery plant is one kind of Orchids, by common name Lady Slipper. "The Rainforest Gardener" at "The Rainforest Garden" further confirmed Lady Slipper orchids are in the Paphiopedilum genus.
Thanks, FloridaGirl and The Rainforest Gardener! It is very nice of you to spend time to identify this plant for me!