i didn't need one for Singapore and neither should you but you need to confirm that for yourself. There is a requirement for all travellers to Singapore to complete an online arrival card with health declaration and there is no waiting period.
I think you can do it in the airport as you arrive.
Singapore is fantastic but expensive for hotels.
The Vietnam online evisa took 4 days and I enjoyed every moment of it too!
i had previously held a 1 year visa for business and was able to open my bank account and get the driving licenses.
I still visit a few times each year and the bank just wants me to show up with my passport so they can take s copy however the dp can't be renewed without a long term visa.