To create Thai pleats, make a drapery panel with a double-fold heading at the top. The amount material used in each pleat needs to be twice the depth of the heading, for example; if using a 4" double fold heading, allow for 8" in each pleat. Fold-in the pleats and sew the bottom half vertically, stopping at the bottom of the heading.
The photo above shows that the top half of the pleat is "open", and not sewn as you would with other pleats; which are sewn all the way to the top.
Gather or pinch at the base of the pleat and tack, using a doubled thread
After the bottom of the pleat is tacked, stab the needle through the top of the pleat, at the center, and pull the thread to bend the top of the pleat down.
This stripe sheer drapery with Thai pleats is shown hanging on Aria™ hardware from Finestra® Decorative Hardware. The photo at the top of the blog features brushed brass pole rod, rings and ball finial. The photos at the bottom of the blog features brushed brass pole rod, rings and plain end cap.
For easy installation, clip-on rings can be used. The clip will be hidden inside the pleat.
If rings with eyelets are used, drapery pins can also be inserted into the back, stitched-are of the pleat.