I want to grow some rocket, or as we call it arugula.... any body know FOR SURE where there are seeds for sale?  

Try the big building at Worawot market.  Many large and small seed merchants can be found in the basement and ground floor.

I found Rocket in Wororot market.

Close to where they sell frogs & turtles from open bowls.

There was only 1 brand of seed, germination was terrible, less than 5%.