Bats, bats, bats... How bad?

Rude awakening yet again. First thing I woke up to was not a greeting of 'Good morning'; rather an exclamation of 'Bats! Again!'.
There was a bat on the loose in my home, not a cave.
Well luckily it was not in the room I was sleeping in, unlike last week.

Last week....

Dad was outstation. Left mom, and me, and of course Yati.

Tuesday: Morning - A monitor lizard on the loose. Chased into the monsoon drain in the backyard. Evening - Sighting of the first bat. Took quite an effort to catch it. Mom and Yati were waving the broom frantically in the air, trying to hit it the air-borne bat.

Wednesday & Thursday: Caught another three bats upstairs. One of course was sighted the first instant I opened my eyes.

Weekend: Thought the bat caught on Thursday was the last I'll ever see in the house. How wrong I was! Unknown to me, while I was in KL, dad caught one more.

So today... Yet another, bringing the total to 6 bats. What's going on? We can never be certain they were the same bat(s) because we didn't kill them all. What a mistake... The question is: How did they get in? When?

It remains a mystery, yet to be uncovered.