@Ahmad, what assets that we have after 2030 that you will think have more than enough 'parity' to 'theoritically' invade Singapore, relative to what Singapore has by then in 2030 ?
Let's see,
By 2030, if what the planners plan come to fruition TNI-AU probably have 10 Fighter SQ, 6 medium Transport SQ, 6 Light Transport SQ..which Fighters probably consists more of F-16 including the V and some Flankers.
That will not be enough to invade Singapore which consists of F-15E, F-16 (that some already upgrade to V standards), and by that time already 1 operational SQ of F-35.
How about Navy, probably by 2030 we got many LCU, 12-16 LST and 8-12 LPD and if the planner got what they plan 1-2 LHD (that PAL already prepared the design). Seems large enough Amphibious assets to move one division, but as the largest archipelago we always have relative large Amphibious force. How else we move around forces between island.
However to used that to invade Singapore, we need those amphib to be escort with enough ASW Frigates/Corvettes (say 24) and at least 6 AAW Large Frigates.
Singapore Navy will at least by that time also build enough Frigates and Corvettes/Litoral forces to handle invasion forces of 6 Large AAW and 24 ASW.
Those 6 Large AAW and 24 ASW is the most we can have by 2030+, "if" we build enough budget and Industries support.
Thus by their AF and Navy in 2030, Singapore still maintain enough parity to their neighbors to make it hard any regional powers (and that Includes Australia or India) to launch invading forces.
Singapore knows their livelihood depends on trade and that means they have to make anyone think twice to invade them.
Something that even Soekarno, did not plan to do. Despite some historian says Soekarno have Territory ambition on 'Konfrontasi', I have seen enough documents that saying otherwise.
Soekarno did not have plan to Invade Malayan peninsula or Singapore. He wants British and Australian forces preoccupied defending Malaya and Singapore, while he can support 'leftist' North Borneo forces to control Sabah and Sarawak to create their own 'revolutionary' state independent from British influenced.
I put it in here, cause even at that time Soekarno know that it need large 'Global power' to invade Singapore. Japan is large global military power in WW2. Thus in this scenario only China or US that has enough power to send invading forces to Singapore.
Add:
Any invasion to Singapore in my opinion need to do what Japanese done in WW2. That's invade Malayan peninsula first. As in WW2 with British make Singapore as 'fortress Singapore', at the moment Singapore also make their defense in sense as 'fortress'. However Singapore seems learned what British failed in WW2. To defence Singapore, you have to be more mobile and do preemptively.
Let's see why I put even India is not sufficient enough (even in 2030+) to invade Singapore. If by that time (as plan) India will have 3 Aircraft carriers, but their CV is smaller than US CVN. At most Indian CV altogether can only provide 5 SQ of fighters bombers. That only enough to provide air cover for Invasions force.
Let's see what Japan done when they want to take Fortress Singapore, they done (even with larger CV force than India now or in 2030), by landed in peninsula and work down from there. British force eventough fight on peninsula, but enough of them are stay in Singapore to guard potential invasion from sea (which Japan had not done it because it's much more riskier).
Thus if a force like India (which is larger than Indonesia now or in 2030+), will have difficulty to launch invading forces from sea as Japan face in WW2. Then they have to land in Peninsula.
This in sense talking about Indian force has to 'pacified' Malaysian Armed Forces or Malaysian Armed Forces has cooperate with Indian Forces to invade Singapore. In that case Singapore force I bet will not stay waiting in Singapore..but will take preemptively to fight in Peninsula outside Singapore.
Again I put this 'scenario' just to show unless you (the invading force) are a 'Global' power, Singapore by them selves still have enough power to defend it self.
All of this off course in scenario where US already completely taking itself from Global power and only stay home. Where everyone else have no 'alliance' left and has to defend it self.
Even then I do see Singapore' still able to defend it self from other neighbors or regional powers.
It will be different if we talk about China, with US gone and they manage to completely armed their whole 'man made' island in SCS with 4 CV and 2 CVN as many predicted China will have by 2030+.