The only left hand drive vehicles you might have seen in Singapore would be diplomatic plates, and those will be re-exported when the owner leaves.
You might try the official exporters found on the onemotoring website but I doubt they will be of much help.
https://www.onemotoring.com.sg/content/ ... ointed_EPZ
I doubt you are going to escape tax on your Myanmar vehicle just because you are going to personally import it. Like Singapore, Myanmar appears to imposes taxes and fees on personally imported vehicles, such that your costs will be nearly the same as if you had purchased there. You should verify this before proceeding with your importation plans.
Finally, within the region, Thailand is the only place in the region you will find significant numbers of left hand drive cars, even though it is a right hand drive country, mainly due to its proximity to Myanmar, Laos, and Cambodia, all left hand drive.