Reading some of the posts just makes me laugh at how poorly thought out they are, especially the ones about the Su-30 v F-15 argument. After reading the entries, I wanted to contribute my own thoughts and feelings so that new posts in this thread will not be just some patriotic banter from some other neighboring country. All the information provided can be found on the web if you bother to look it up.
FACT
1) Singapore is rich, richer than any other country in the region. The government is well-run and led by very smart forward looking people, corruption is also generally very low. Thus it is safe to say that the Ministry of Defense is also very competent and they always think things through from every possible angle before they make decisions. The F-15SG was bought simply because no aircraft which was available can fly further, faster, higher, carry more bombs and provide more value for money with a proven combat record. The Su-30 is cheaper and less advanced, the Rafale and F-18 just couldn't match the F-15 in performance. Thrust vectoring really isn't as effective at BVR then you would like to think it is, it is only nice for airshows and dogfights provided you can even get that close.
2) Singaporeans are generally already well educated and tech savvy, they may lack hardiness and so called "combat-fitness" but i assure you, they learn fast and will adapt to new skills and equipment to a proficiency just as well as or better than anyone in the world. In the area of military aviation, brain power is a hell lot more important than physical ability because technology is such an important factor here.
3) By pure numbers alone, the RSAF has more combat aircraft than any other air force in SEA even with some assets overseas. Every airmen is trained to a very high degree of proficiency both at home and overseas, we don't get invited to Red Flag exercises every year for no reason.
4) The RSAF has an in-flight refueling capability for all the combat a/c it operates and has operated AEW platforms since the 80s. Thailand has only just become the 2nd operator of such platforms in the region. Do not underestimate this capability because it allows the airforce to coordinate all its aircraft and handle threats more efficiently.
5)The RSAF has an exemplary safety record which means more aircraft are available to fly at anyone time with minimal turn around time. Because we operate equipment with ample spares and parts commonality, we don't have much trouble maintaining our platforms. Can Malaysia or Indonesia say the same of their operational readiness? When the Indons bought the Su-30, they couldn't track the aircraft because the russian systems had no compatibility with the western systems they used.
6) Some of the weapons systems do not exist in any of the other inventories of the region eg. AESA, GPS guided munitions, Sniper Pods, Longbow.
Summary: There really is no contest here, every defense journal, publication, report states that the RSAF is the most capable and therefore most powerful Airforce in SEA. All the points listed support that notion and as you can see, it is more than just a platform vs platform argument.
When you bring in the equipment and capabilities of the navy and army, you will also see that as a whole, the Singapore Armed Forces is leap and bounds ahead of any military in the immediate region.