not that hard, just make better warships then they have, and send them to auto attack to eliminate all their worthless forces. quite simple. you don't want to provoke them to fight you before you are ready though, that would cause unnecessary problems. don't forget to espionage, with an empire as large as theirs, if you can power down all their economic buildings, it will eventually contract their standing forces. when i get threatened, and i know i can't beat a civi militarily i just keep trying to build ties with other civi and tries to espionage the crap out of the opposing civi. 40 agents would get that jobs done, not to mention you get some of their techs on occasions

Well for the most part the AIs fight cold war not a war what this means in a war the AIs instead of fighting build bigger fleets. If U time this wrong your screwed the Thalans like the other AI's declare war before they R ready they will declare war and then modilize that means for a long time they won't attack untill U attack them but when they he better ttack if U dont attack early it will be with transports. What will also help U is at the start of the game part of the Thalans strength during the game is sucky AI's like the Dominion of Korx, the drengin, the Arceans, the Yor, the Drath, the Altarians, and the unchanged Korath clan. By these AI's not expanding it gives the Thalans room to expand So instead put the Korath clan abilities should placed in economics morale and population growth with a generic Ai This will mess up the Iconians but it will be worth it and U should customize oppenents with either the Krynn or generic AI's Thcustom racese better opponent will limit the Thalans make sure the Torians, Modified Korath Terans and the Krynn join the Thalans with custom races one suggestion is a super hive with a torian tech tree. before U war make sure to get the Thalans morale techs other than that I don't have any other advice what I have given U will cause the Thalans longer to build up