Only allowing 2 hrs 30 mins to connect between 2 flights at Changi Airport Singapore is cutting it fine?

There is no scheduled flight from IPH to KUL or PEN. I'm just curious,  if my IPH/SIN ticket is MH-marketed (MH codeshare), would I be able to interline my luggage to my final destination considering MH is part of Oneworld? 

Enojet Interline agreements have nothing to do with Alliance agreements, often interline agreements exist between competing carriers (I have interlined between TK, AZ and BA and all tickets were on seperate bookings, had no issue at all). Interline agreements have got more to do with seperate contracts between airlines. Often low cost carriers do not participate 9it does bring extra cost) however, since Firefly codeshares with MH and has interline agreements with MH, I would think they are also able to interline with QF since their booking / check in system can handle interlining luggage.

Seriously not pushing it, yes ofcourse you can have a delay, but in all honesty you can do it in 1.2 hrs easily. It has never taken me more than 30mins to clear immigration and pick up luggage in Changi and that is coming from lionghaul and regional flights in lowcost and full service carriers. Changi is efficient and baggage handling and immigration are superfast. I am seriously puzzled why one would think it is not achievable.

If all the stars align and the OP goes to Kwan Yin Temple in Ipoh to pray for good travel luck, then it will work. The problem is that if the Firefly flight goes sour, the entire trip goes out the window.

Remember - the OP has 150 minutes to execute the entire connection, presumably including minimum check-in window. OP is also on the last IPH-SIN flight of the day, and unless they are connecting to QF 6, the QF leg is also the last of the day.

No matter how much I love Changi Airport, my stance is still that the OP should err on the side of caution and take a longer SIN layover. In the worst case, this results in multiple plates of fish ball noodles in the basement. If the 150 minute connection goes south, he or she will be STUFFED. (And not with fish ball noodles.)

you should have 2 hours spare! hey guys remmeber me i made that daring 1hr 30 layover in DXB, even after changing from emirates terminal to t2.  AND we got parked out on the tarmac and bussed it in....

must say the emirates 'tarmac bus' for first passengers was a real treat!

I did the same thing last week but chose the morning flight out of Ipoh to give plenty of connection time. The afternoon flight is sometimes quite late into SIN due to traffic delays in SIN. It seems to compound as the day goes on.

Really comes down to what kind of person you are. If you worry a lot, just book a different flight. Yes there's a risk, there's always a risk. I once had 3 hours between flights at JFK and my first flight was delayed by 3 hours and 5 minutes due to a snow storm. And your travel insurance may not cover it. 

Objectively I think its very unlikely you'll have any problems, but if you're worried about it then you'll be stressed about it the whole trip, so just change it. 

If like me you hate being time inefficient and don't stress about 1% occurences, then no need to change.