Flying between KUL and PEN on Malaysia in Business yield 40 British Airways Executive Club Tier Points, and costs only £50-55, which is a very attractive £1.25-1.38 per Tier Point.
If I book multiple one-way flights on the same day, between the two destinations, will I be allowed to fly?
For example:
Yes. There is the possibility you'll be questioned as to your motives, but in the end they're all domestic flights, so it's down to you and the airline for the transaction, and they've sold you the tickets.
Of course, the Earth might not thank you ;)
I know of a role here in Sydney which requires employees (non-airline) to fly 6 flights in a day, with flights 2, 4 and 6 returning to the same city. It's a regular feature for people on the team, and they're never prevented/questioned about it, except by the crew who can start to recognise them :)
Yes. The airline is a business, they are happy to receive your repeat custom.
Your concern should be whether this is feasible: if the same aircraft is used to operate all flights, then one flight delayed will not impact the rest of your itinerary, because the subsequent flights will also be delayed. (This is called a "back-to-back" in mileage running terms.) If different aircraft are used, then one delay could scupper the rest of your itinerary.
The second problem is that the British Airways Executive Club has difficulty understanding flying the same route on the same day multiple times; i.e., you may only end up with one set of tier points. So keep your boarding passes as evidence you flew multiple times and retroclaim if needs be.
Finally be aware that if this fare books into "I" class, it will earn zero Avios and zero TP on BAEC. If it books into "Z", you are okay.
Enjoy your trip.