With the same wattage bulbs as are in there with the turn signals, you wouldn't need a relay, but you could add one if you really like the extra work. Now if you wanted to put high wattage bulbs in there, you would need to build your own housings because the factory ones are plastic.
I've thought about doing a little different mod, but I'm waiting until I get a new bumper because mine is damaged. I'm going to try and replace the sockets with ones that hold 2 fillament bulbs. I would run the 2nd fillament to a switch to use as running/fog lights and the other fillament would be used just as stock for turn signals.
Here's a tip to convert your corner lights to blinkers.
First, get Ford 1157 sockets with a ground tap and use a dremel tool to make the opening bigger. Next, slap in the 1157 socket and secure all around it with silicon sealant. Tap the hi current (blinker) to the bumper light's power wire with T taps, then tap the steady to the original parking lights that were existing in the corners.
Ground the tab and you have useful blinking corners.
If you wanted high wattage fog lights there, here's what I'd do:
Take the factory housings out and cut out the front and put in a pre-made set of fogs. This way you wouldn't have to re-make a custom lense which would be very difficult unless you know a lot about lenses optics, and plastics. I've seen it done on a Jeep for back-up lights before, so why not on a Tacoma's front turn signals? Basically you'd have a set of PIAA or some other make fog lights (in housings) flushed into the stock Toyota lenses that you cut out. It won't be easy. Personally I'd just keep convert the stock lenses to low wattage running lights and install the real fog lights elsewhere in the bumper, but give it a try if you're feeling ambitious.