Lasaga scored twice in the first half for Tauranga West to give them a 10-5 lead at the break, with East hitting back via a disputed try.
A superb 75m intercept effort to East's Louis Grindrod early in the second half levelled the scores before rampaging No 8 Joshua de Koster barged over for two tries, both converted by Kata Brill, to give West breathing space.
Kingi said he was worried at 10-10. "We played them [East] pre-season and beat them but expected a tough one and they came out mean fighting."
Te Puke qualified top in round-robin after an unexpected 61-0 thrashing of Opotiki, including a 47-point haul in the second half, while West were second after a crushing 46-0 win over Whakatane.