My experience is that most of such things (e.g. the VOA and customs declartion for Indonesia) can be done online. SIN apparently even has an app. I bit of googling around will go a long way. I usually check the Dutch foreign affairs travel safety by country pages to see what admin you have to do beforehand - guess most foreign affair website in most countries will have pages with recommendations by country.

See e.g https://www.ica.gov.sg/enter-transit...g-arrival-card