I think China shouldnt waste their time on Singapore. Forget that 75% of singaporean are ethnic Chinese. Most of them don't have any special feeling for China. China likewise shouldnt see them as Chinese but Singaporean.Again, Singapore is dependent on USA for security, because it had too. So, it's military leadership is tight with US military. There is no way in a US/China conflict, Singapore will allow US to use any of its military installations. Remember, Singapore's biggest fear is that Han Chinese people losing its majority share of Singapore population. It has seen what happened in Malaysia when Han Chinese share of the population drops. It's entirely dependent on the supply of Chinese people from Malaysia and mainland.
When China has advanced weapons that it can sell to Singapore, we will see what happens.
Should China prioritize Indonesia and Malaysia over others in the region? Of course. They are much bigger fish and are not being offered stealth aircraft by anyone else. China can also offer to build up local EV and renewable industries for greater influence. With Australia looking to turn itself into regional superpower, Indonesia should feel very threatened. It is the biggest catch in the region. Again, China will have a lot of weapons it can offer to Indonesia by the end of this decade. As Indonesia grows, it should no longer have to bow down to Western countries due to military weakness.
Remember singapore was the last country in the region to established formal ties with china. It deliberate policies of waiting for Malaysia and Indonesia to do so before they follow.
Hence If china wants to bring bilateral relation to a new height with Singapore, they should just put singapore one side focus in Malaysia and Indonesia instead. That will put tremendous amount of pressure on Singapore gov to improve ties