Tien is at least as strong as Frieza end series. He showed no reason that he would stop training, and I'm completely basing this off Supreme Kai's statement of "The Kais could defeat Frieza in one blast" Supreme Kai, is one of those Kais, and he got destroyed by Fat Buu(The weakest form of 'evil' Buu mind you), and Tien, while he didn't do much to Super Buutenks(2nd strongest form of Buu), he did survive a kick. Which is something.
Maybe not 100% Frieza, but I think Tien would put up a good fight. Krillin and Yamcha would both die pretty quickly to Frieza.