"toi" can stand for "tuo" in spoken Finnish. The sentence decides its meaning.
Kato, toi on mun kaveri. - Look, that's my friend.
toi here: that - spoken form of 'tuo'
Written Finnish: Katso, tuo on minun kaverini.
Paljonks toi maksaa? - How much does that cost?
toi here: that - spoken form of 'tuo'
Written Finnish: Paljonko tuo maksaa?
Onks toi juna? - Is that the train?
toi here: that - spoken 'tuo'
Written Finnish: Onko tuo juna?
Toi on mun paras kaveri. - That's my best friend.
toi here: that - spoken 'tuo'
Written Finnish: Tuo on minun paras kaverini.
Ota toi kassi. - Take that bag.
toi here: that - spoken 'tuo'
Written Finnish: Ota tuo kassi.
Toi istuu sulle tosi hyvin. - That fits you really well.
toi here: that - spoken 'tuo'
Written Finnish: Tuo istuu sinulle tosi hyvin.
Spoken and written Finnish are different registers. The examples show how "toi" is used here and pair it with the written sentence. Learn the meaning in context rather than replacing every occurrence of a word.