When Matthew's party travels to Ayuthay, they are faced with the obstacle of crossing Barai Pond, as there is no rowman to carry them across, despite a large number of Kaocho soldiers hanging around. However, the Adepts are able to use their Psynergy to cross via a series of rafts and lily pads.
After entering Ayuthay, the Adepts learn that Barai Pond is a man-made reservoir that is meant to hold the runoff for the Alchemy Well. Prior to the well's reactivation, the pond's water-level was much lower, allowing access to Barai Temple. According to King Paithos, the temple is now underwater due to the immense amount of water the Alchemy Well produces. This is a problem as the Adepts will need to explore the temple to find the Insight Glass, a treasure necessary for their current quest to restart the Alchemy Forge in Passaj. Luckily, however, the Adepts are able to use the Sand Prince Stone, which they find in Ayuthay, to reverse the flow of the Alchemy Well. This lowers the water level of Barai Pond, allowing access to the temple. After finding the Insight Glass, the flow of the Alchemy Well is restored, raising the water back to its normal levels.
After the Adepts leave Ayuthay, a Kaochan soldier is now available to ferry the Adepts across Barai Pond.
When first arriving at Ayuthay, the area is flooded with Kaochan soldiers, who literally are just standing around, having no orders or ideas as to the location of the Ayuthay residents. Two soldiers near the entrance will block the way to the pond. To the left of these soldiers is a barrel containing an Herb, while to the right is a jar with an Antidote.
Speak to one of the guards, and show the Wo's Letter received in Kaocho. The guards will allow you to pass, but note that there is no rowman available to carry you across. It is possible to tell them you are not there to help them, but they'll still let you by.
After the guards is a raft which can be navigated around the pond. To control the raft, you have to cast Whirlwind in the opposite direction of where you want to go. This first raft does not have very many travel options, so just go up and left. Use the lily pads here to jump over to the landmass. Climb up the skinny tree to find an Apple. Look to the right and find another raft.
Get on this one and go up and left to get to the chest to claim a Cookie. The north exit leads nowhere, so get back on the raft and travel right and down, then right and up. Go up the north path.
There is a Jupiter Djinn right off the bat with no way to get it. Head up and show the guards the letter. Follow him into the door. Here you'll meet the two Kaocho generals: Ku-Tsung and Ku-Embra. After reading your letter, they leave, having given the order clear out the evil spirits in the place. At this point, go and find the tree that houses the secret entrance to underground Ayuthay.
The north path is closed off for now, so take the right path and go outside. Grow the plant and go through the door on the left. In here, take the right path and continue on to get back outside.
Leave Ayuthay by the south exit and find another raft. Jump on it and go to the left to get that chest and some Leather Boots. Now shoot yourself right, down, and right again to get caught up in some lily pads. Use them to push the column to the south down into the water.
Jump up to the landmass to the north and get on the new raft. Shoot yourself down and then left, and then down to get the Glittering Tiara from the chest.
Shoot yourself up and left, then up, left, up, and right. Ignore this first ladder and use the lily pads to get to the second one and go up a screen.
Now go back the way you came and use Arid Heat to enter Barai Temple.
Herb: found in a barrel near the initial entrance to Ayuthay.
Antidote: found in a jar near the initial entrance to Ayuthay.
Apple: found in a tree on a small landmass in the center of the pond. Climb up the tree to automatically collect the Apple.
Cookie: located in a chest near the northeast corner of the pond
Leather Boots: found in a chest after the water level is lowered.
Glittering Tiara: found in a chest on a small landmass after the water level is lowered.
Water of Life: found in a chest at the northwest part of the moat outside of the main building.
Jupiter Djinni Breath: found on a lily pad near the entrance to the main building. Cannot be approached until after the water level is lowered.