River Tay
The River Tay emerges from Loch Tay at Kenmore, and flows from there to Perth which, in historical times, was its lowest bridging point. Below Perth the river becomes tidal and enters the Firth of Tay. The largest city on the river, Dundee, lies on the north bank of the Firth. On reaching the North Sea, the River Tay has flowed from west to east across central Scotland.
Sai River (Thailand)
Sai River (; ; ), formerly known as the River of Lawa (; ), is a river that forms the natural border between Thailand and Myanmar at Tachileik and Mae Sai Districts. Mae Sai town, where the bridge crossing the international border is located, is named after this river. It is a tributary of the Ruak River, itself a tributary of the Mekong.