Sinhalese chain stitch is a variation of the square chain stitch / open chain stitch. This stitch creates a quick and simple two-toned border.
Anchor the base to fabric like shown below.
The base will have two parallel lines hanging down.
Bring the second color thread at A. Pass the needle under the base like shown below.
Go down at B and come up at C.
Repeat by passing needle under base stitches. Then go down at D and come back up at E.