Tongan spelling is phonemic, it is spelled the way that it sounds.
a as in father (only shorter) fala, mate, pato
ā a lengthened mālō, kākā, fakahā
e as in bet (or somewhere between bet and bait) fale, mele
ē e lengthened pehē, ko ē
i as in machine liku, piko, taki
ī i lengthened ī, kulī
o as in born (pronounced a little farther fono, pito
back in the throat)
ō o lengthened pō, kokō
u as in root (only shorter and without offglide) lotu, muka
ū u lengthened pūluhi, fufū
In Tongan all consonants are separated by a vowel, all words end in a vowel.