This description of how stakes were planted in rivers for defense comes from the later part of Razadarit Ayeidawpon (San Lwin’s unpublished translation):
Extract 2: Battle of Pannin (c. 1416)
Around the time that Ava was occupying Khepaung, Ava’s ally Toungoo sent forces south along the Sittaung river. These forces were intercepted at Paninn by Mon forces from Salat. In the battle between Salat and Toungoo, Salat had the upper hand, but at the end of the day both sides retired to their camps located on sandbanks on opposite sides of the Sittaung river.
Toungoo made defensive preparations by driving a double line of stakes into the river in front of their position. The first front-most line was concealed below the water; the second line in back was visible above the water, probably to lure the attackers onto the first line and their destruction. When the Salat warboats made an assault against the Toungoo position at dawn the next morning, these stakes punctured and ruptured the hulls of the attacking boats, sinking them (San Lwin, 131-132).