Ok, here goes... The frame is composed of one basic shape, shown in the first image below. I created it using the Pen Tool, carefully tracing from the sample that the OP provided. Create this shape on its own layer.
Copy this to a new layer and transform (flip) it both horizontally and vertically. Use the Move tool to position it like the image below. Then merge these two layers. (Copy this layer to a new layer and call it BackUp. De-activate the BackUp layer for now, but we'll need it later.)
Copy this layer many times and use the Move tool to create a string of them of whatever length you want. To keep things organized, it's a good idea to group of all these layers once you've created the right number of them.
The sides of the frame are the same as the top, but the basic shape is rotated 90 degrees counter-clockwise. Create a new verticle string of shapes and position them as below to create the sides of the frame. Group all of these vertical layers as Group2. (In a minute, you'll need to nudge Group2 to get it precisely in the right spot, but for now just get it close to the image below.)
Now comes the hard part. The corners of the frame have a transition that uses the same basic shape, but some layer masking will be required. There are two shapes we'll need to make, which will be shown in blue and green so that you can see them clearly. First the blue one: use your BackUp layer that you saved earlier and copy it to a new layer. Flip it horizontally and rotate it 90 degrees counter-clockwise. Now move it into position so that it lines up nicely with the top edge of the frame to create a smooth curve. It should look like the blue shape below. Now go back to Group2 and use the Move tool to align it nicely with the blue transition shape. Don't worry about the overlap—we'll mask it later.
The last piece also uses the same basic shape, which I've shown in green. Make another copy of your BackUp layer and rotate it 90 degrees clockwise. Move it into place as shown below.
The last step is to apply a layer mask to both the blue and green shapes to mask-out the parts we don't need. The final result is below. Once you've created one of these corners you can copy the entire merged shape and rotate it to create the other three corners.