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This thread is on the Hong Kong Forum and although it is talking about moving a Tesla from HK to the UK many of the issues are relevant to your situation. Primarily is the fact that Tesla will not support a car purchased for one region in another region, even if they have a presence in the destination region. The other main issue is maps are only installed for the region of destination and because of the first reason, getting them installed on your car is difficult to impossible.
The loss of maps doesn’t stop you driving a Tesla but limits any range prediction and other features. Finally if something does go wrong you run the risk Tesla may not sell you parts, even if you can find a willing repairer.
Having said all that, a Hong Kong spec car is probably the closest to what Tesla would sell in Singapore as you are both RHD countries with UK style power infrastructure.
EDIT
Looks like Tesla may be in Singapore soon if this article is correct, however it seems the Singapore Government is not exactly welcoming them with open arms. Tech in Asia - Connecting Asia's startup ecosystem