As other reviewers found it hard to find, first about the location
Luangpho.street has a street sign where it reaches the riverside. From Maharaj street is is the sidestreet opposite the Shell petrol station. The restaurant is on the south side on the eastern block.
It's a small place with the sort of lunch buffet you'd expect. Tastes delicious. Slightly more expensive than simular restaurants but still dead cheap.