Between Exhibition and Spring. Just get train to Parliament or tram to top of Bourke St and walk down the lane by Pellegrino. I always stay just across the street from Longrain but I've never been in there yet!

Sydney is far better for cheap Thai in the centre; I wouldn't bother looking in Melbourne CBD but obviously OP is a Man on a Mission.

Can I put in a plug for Horoki in case you trek to Longrain and don't like the prices?

One of several "Japanese tapas" bars around that end of Melbourne these days, they have some hits and some misses but definite hits for me are the diced Scotch fillet and the almond-encrusted prawns (shrimps to Americans, apparently, if the Paul Hogan ads were targeted right).