Rad Na literally means "pouring over", which tells how the dish is made in the final step - pouring the gravy sauce over the noodle. It's an outstanding one-dish meal, a very good lunch or late-night dinner. Although not necessary, a good wok is preferred to make this dish.  Cooking a stir-fry dish at home is quite challenging because the home stove / cook top won't give enough heat to sear the food.  We overcome this problem by using a thick cast-iron wok which retains heat very well once we put cold food inside.  I have been using the Lodge Pro-Logic cast iron wok for a while and really enjoying it. 

The highlight of this dish is the tendered pork marinated overnight.  If you eat this dish in Thailand, you'll know what I mean.  It's really tender yet giving some texture that is unlike melting-in-your-mouth.  I did a lot of research and found a bunch of tips.  Some recipes call for corn starch.  My chef and my mom said egg white.  Another blog says baking soda does it.  I say why not do it all.  So below you will see the recipe for my version of the marinated pork.  Try it, and you will love it.  Don't put too much baking soda though or you will get some bitter pork.  
Marinated Pork
Lodge Pro-Logic Cast Iron Wok
Marinated Pork for Rad Na
(serve 2)

one big piece of pork loin, about 3-4 lbs, sliced across the grain into about 2 mm thick slice
1/4 cups oyster sauce
1/2 tablespoon salt
1/2 tablespoon ground white pepper
3 tablespoons light soy sauce (ซิอิ๊วขาว)
1 egg white
2 tablespoon corn starch
1/4 teaspoon baking soda
Marinate over night
Next up is the noodle.  We use fresh flat rice noodle, and we cut them manually into about 1-inch stripes.  They may come stick together in multiple layers, and we should pull them apart by hand.  Then, we will stir-fry the noodle with an oyster sauce and a dark soy sauce.  The wok has to be very hot for this task, so go ahead and heat whatever wok you have on high for sometimes.   Use little oil, and it should smoke right away when you pour it in the wok.  Add the noodle, and add the oyster sauce and dark soy sauce all over them.  Leave the noodle on the work for a while before you try to stir them.  You want to sear the noodle.  If you stir them too much, the rice noodle may break apart and turn into a ball of mess.  So resist your urge to put your spatula into too much action.  Once the noodle is seared enough and all covered with the sauce, remove from wok and set aside.
I like this brand.  It's sold uncut.
After it's cut into 1-inch stripes and pulled apart
This is how much I added the sauce
Finished product - set this aside
Next we should go prepare the Chinese Brocolli, called Gai Lan.  Of course you can substitute brocolli if you can't find its Chinese relative.  If you use Gai Lan, separate the leaves and the stems.  Peel the outside of the stems and cut them into slices.  
Rad Na with Pork Recipe
(serve 2)

For the noodle
1 package of fresh flat rice noodle, cut into stripes and pulled each strand apart (1 lb)
2 tablespoon of oyster sauce
2 tablespoon of dark soy sauce (ซิอิ๊วดำ) 

For the gravy
16 oz of the marinated pork
1 tablespoon of chopped garlic
1 cup of chinese brocolli stems, peeled and cut into slices
2 cups of chinese brocolli leaves
1 1/2 tablespoon soy bean sauce
1 tablespoon light soy sauce (ซิอิ๊วขาว)
2 tablespoon all purpose seasoning sauce
1 tablespoon dark soy sauce (ซิอิ๊วดำ)
1/2 tablespoon granulate sugar
chicken stock or water as needed
2 tablespoon corn starch (or maybe more)
(from left to right): Dark Soy Sauce (ซิอิ๊วดำ), Light Soy Sauce (ซิอิ๊วขาว), Oyster Sauce, All purpose seasoning sauce and Soy Bean Sauce
Start with garlic oil
Add the marinated porks
Add Chinese Brocolli and soy bean sauce
Then add the stock.  Plain water will work too!
Now you are ready to make a gravy sauce.  In the same wok that was used to stir-fry the noodle (don't wash it), add oil and saute garlic until it turns gold.  Add marinated pork and stir-fry until it's cooked.  Add the stems part of Chinese broccoli and soy bean sauce and sugar.  Stir-fry until they are mixed together and sugar dissolved.  Add water to cover everything in the wok.  See picture below for how much you should add water.  Season with light soy sauce and dark soy sauce, and add all purpose seasoning sauce to taste.  The flavor profile of this gravy is salty and very subtle sweet and tart.  Go ahead and season until it's too salty for you, because it will become less salty in the next steps.

Prepare your slurry by mixing corn starch in little water until fully dissolved.  Add slurry into the wok to thicken the gravy until you get a desirable thickness.  Taste again and adjust the seasoning.  Add the Chinese brocolli leaves and cook for another 30 seconds or so.  You don't want to overcook the leaves.

And here we are, plate the noodle, and go ahead and perform the final step - Rad Na....
After adding slurry, the gravy should be thickened so it will coat the noodle well
Plate the noodle
Don't forget to toast the spice first
and pour the gravy mix on top
The final product will have a saltiness and subtle sweetness from the gravy, bitterness and crunchiness from the Chinese broccoli (so don't overcook them).  Strong umami from all those soy sauce and seared noodle.  It lacks some sourness, so vinegar will brighten the dish big time.  In his popular book Ad-Hoc at home, Thomas Keller suggests we learn to use vinegar as a seasoning device.  Now is a great opportunity to practice that.  Basic white vinegar works so well here.