Combine all ingredients except for the meat and scallions. Whisk to combine. Pour over the london broil.
Cover and refrigerate for a few hours or overnight.
If desired, sprinkle sliced scallions over the meat before broiling.
Place the meat and marinade in a (9x13) pan. Broil on high for 7 minutes. Turn it over, then broil an additional 6-8 minutes, depending on the size of the meat and your desired level of done-ness.
Let meat sit for about 5-8 minutes before slicing.
To reheat: save the liquid after broiling the meat, and reheat in the same liquid. Careful not to overcook the meat.
Recipe by Overtime Cook at https://overtimecook.com/2015/03/12/thai-marinated-london-broil/