@Sansan24 it is likely that it is just shedding the oldest leaves, since the bottom leaves are the ones turning yellow. As you noted it sounded like the plumeria was outdoors but has been moved indoors. It does react by shedding its old leaves when moving from outside to air conditioned room. But it is also possible that the soil is holding more water, and staying wet longer indoors.
If it has been indoors, let it slowly acclimate to direct sun. The leaves could easily get sunburned if you move indoors to outdoors.
Judging from the photos you live in a high rise condo. So if I recall it could get too windy, so once your plumeria is taller you will need to anchor the potted plant or get a heavier pot (and still anchor it).
Also rainy season begins late July to November/early December but since there is no frost you can leave the plumerias outdoors all year round. Plumerias love direct sun and will thrive and bloom when given 6 to 8 hours of direct sun.
I do the skewer and lift test until the plumeria is at least 9 months to a year old then pretty much it needs less care once it is established.
Plumeria loves rain water. So once it is established it can handle the daily rain so long as the drain holes are unclogged. At the current age of your plumeria too much rain can cause root rot. You can cover the base with plastic cover during rainy season.
This is my seedgrown plumeria I named this 'Sampaguita's Curly' since it is white and fragrance reminds me of Sampaguita, the national flower of the Philippines.
Check out desert roses too, and hoya you might get blooms earlier while waiting for your plumeria to bloom. I am only recommending the plants that can thrive even if you are away for a month or longer.
